Apparatus for transmitting broadcast signal, apparatus for receiving broadcast signal, method for transmitting broadcast signal and method for receiving broadcast signal

ABSTRACT

A method for transmitting a broadcast signal proposes a system for supporting a next-generation broadcast service in an environment for supporting next-generation hybrid broadcast using a terrestrial broadcasting network and the Internet. In addition, the method proposes an effective signaling method for covering both a terrestrial broadcasting network and the Internet in an environment for supporting next-generation hybrid broadcast.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the National Phase of PCT International ApplicationNo. PCT/KR2015/014463, filed on Dec. 30, 2015, which claims priorityunder 35 U.S.C. 119(e) to U.S. Provisional Application No. 62/099,209,filed on Jan. 2, 2015, 62/100,916 filed on Jan. 8, 2015, 62/115,589filed on Feb. 12, 2015, and 62/120,297 filed on Feb. 24, 2015, all ofwhich are hereby expressly incorporated by reference into the presentapplication.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to an apparatus for transmitting abroadcast signal, an apparatus for receiving a broadcast signal andmethods for transmitting and receiving a broadcast signal.

Discussion of the Related Art

As analog broadcast signal transmission comes to an end, varioustechnologies for transmitting/receiving digital broadcast signals arebeing developed. A digital broadcast signal may include a larger amountof video/audio data than an analog broadcast signal and further includevarious types of additional data in addition to the video/audio data.

SUMMARY OF THE INVENTION

That is, a digital broadcast system can provide HD (high definition)images, multichannel audio and various additional services. However,data transmission efficiency for transmission of large amounts of data,robustness of transmission/reception networks and network flexibility inconsideration of mobile reception equipment need to be improved fordigital broadcast.

The present invention provides a system capable of effectivelysupporting future broadcast services in an environment supporting futurehybrid broadcasting using terrestrial broadcast networks and theInternet and related signaling methods.

The present invention can control quality of service (QoS) with respectto services or service components by processing data on the basis ofservice characteristics, thereby providing various broadcast services.

The present invention can achieve transmission flexibility bytransmitting various broadcast services through the same radio frequency(RF) signal bandwidth.

The present invention can provide methods and apparatuses fortransmitting and receiving broadcast signals, which enable digitalbroadcast signals to be received without error even when a mobilereception device is used or even in an indoor environment.

The present invention can effectively support future broadcast servicesin an environment supporting future hybrid broadcasting usingterrestrial broadcast networks and the Internet.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention, illustrate embodiments of the inventionand together with the description serve to explain the principle of theinvention. In the drawings:

FIG. 1 illustrates a receiver protocol stack according to an embodimentof the present invention;

FIG. 2 illustrates a relation between an SLT and service layer signaling(SLS) according to an embodiment of the present invention;

FIG. 3 illustrates an SLT according to an embodiment of the presentinvention;

FIG. 4 illustrates SLS bootstrapping and a service discovery processaccording to an embodiment of the present invention;

FIG. 5 illustrates a USBD fragment for ROUTE/DASH according to anembodiment of the present invention;

FIG. 6 illustrates an S-TSID fragment for ROUTE/DASH according to anembodiment of the present invention;

FIG. 7 illustrates a USBD/USD fragment for MMT according to anembodiment of the present invention;

FIG. 8 illustrates a link layer protocol architecture according to anembodiment of the present invention;

FIG. 9 illustrates a structure of a base header of a link layer packetaccording to an embodiment of the present invention;

FIG. 10 illustrates a structure of an additional header of a link layerpacket according to an embodiment of the present invention;

FIG. 11 illustrates a structure of an additional header of a link layerpacket according to another embodiment of the present invention;

FIG. 12 illustrates a header structure of a link layer packet for anMPEG-2 TS packet and an encapsulation process thereof according to anembodiment of the present invention;

FIG. 13 illustrates an example of adaptation modes in IP headercompression according to an embodiment of the present invention(transmitting side);

FIG. 14 illustrates a link mapping table (LMT) and an RoHC-U descriptiontable according to an embodiment of the present invention;

FIG. 15 illustrates a structure of a link layer on a transmitter sideaccording to an embodiment of the present invention;

FIG. 16 illustrates a structure of a link layer on a receiver sideaccording to an embodiment of the present invention;

FIG. 17 illustrates a configuration of signaling transmission through alink layer according to an embodiment of the present invention(transmitting/receiving sides);

FIG. 18 illustrates an interface of a link layer according to anembodiment of the present invention;

FIG. 19 illustrates operation of a normal mode from among operationmodes of the link layer according to an embodiment of the presentinvention;

FIG. 20 illustrates operation of a transparent mode from among operationmodes of the link layer according to an embodiment of the presentinvention;

FIG. 21 illustrates a process of controlling operation modes of atransmitter and/or a receiver in the link layer according to anembodiment of the present invention;

FIG. 22 illustrates operations in the link layer and formats of a packettransferred to a physical layer depending on flag values according to anembodiment of the present invention;

FIG. 23 illustrates an IP overhead reduction process in atransmitter/receiver according to an embodiment of the presentinvention;

FIG. 24 illustrates RoHC profiles according to an embodiment of thepresent invention;

FIG. 25 illustrates processes of configuring and recovering an RoHCpacket stream with respect to configuration mode #1 according to anembodiment of the present invention;

FIG. 26 illustrates processes of configuring and recovering an RoHCpacket stream with respect to configuration mode #2 according to anembodiment of the present invention;

FIG. 27 illustrates processes of configuring and recovering an RoHCpacket stream with respect to configuration mode #3 according to anembodiment of the present invention;

FIG. 28 illustrates combinations of information which can be transmittedout of band according to an embodiment of the present invention;

FIG. 29 illustrates a packet transmitted through a data pipe accordingto an embodiment of the present invention;

FIG. 30 illustrates a syntax of a link layer packet structure accordingto an embodiment of the present invention;

FIG. 31 illustrates a structure of a header of a link layer packet whenIP packets are delivered to the link layer according to anotherembodiment of the present invention;

FIG. 32 illustrates a syntax of the link layer packet header structurewhen IP packets are delivered to the link layer according to anotherembodiment of the present invention;

FIG. 33 illustrates values of fields in the link layer packet headerwhen IP packets are transmitted to the link layer according to anotherembodiment of the present invention;

FIG. 34 illustrates a case in which one IP packet is included in a linklayer payload, in a link layer packet header structure when IP packetsare transmitted to the link layer, according to another embodiment ofthe present invention;

FIG. 35 illustrates a case in which multiple IP packets are concatenatedand included in link layer payloads, in a link layer packet headerstructure when IP packets are transmitted to the link layer, accordingto another embodiment of the present invention;

FIG. 36 illustrates a case in which one IP packet is segmented andincluded in link layer payloads, in a link layer packet header structurewhen IP packets are transmitted to the link layer, according to anotherembodiment of the present invention;

FIG. 37 illustrates link layer packets having segments, in a link layerpacket header structure when IP packets are transmitted to the linklayer, according to another embodiment of the present invention;

FIG. 38 illustrates a header of a link layer packet for RoHCtransmission according to an embodiment of the present invention;

FIG. 39 illustrates a syntax of the link layer packet header for RoHCtransmission according to an embodiment of the present invention;

FIG. 40 illustrates a method for transmitting an RoHC packet through alink layer packet according to embodiment #1 of the present invention;

FIG. 41 illustrates a method for transmitting an RoHC packet through alink layer packet according to embodiment #2 of the present invention;

FIG. 42 illustrates a method for transmitting an RoHC packet through alink layer packet according to embodiment #3 of the present invention;

FIG. 43 illustrates a method for transmitting an RoHC packet through alink layer packet according to embodiment #4 of the present invention;

FIG. 44 illustrates a structure of a link layer packet when signalinginformation is transmitted to the link layer according to anotherembodiment of the present invention;

FIG. 45 illustrates a syntax of the structure of the link layer packetwhen signaling information is transmitted to the link layer according toanother embodiment of the present invention;

FIG. 46 illustrates a structure of a link layer packet for framed packettransmission according to an embodiment of the present invention;

FIG. 47 illustrates a syntax of the structure of the link layer packetfor framed packet transmission according to an embodiment of the presentinvention;

FIG. 48 illustrates a syntax of a framed packet according to anembodiment of the present invention;

FIG. 49 illustrates a syntax of a fast information channel (FIC)according to an embodiment of the present invention;

FIG. 50 illustrates a broadcast system which issues an emergency alertaccording to an embodiment of the present invention;

FIG. 51 illustrates a syntax of an emergency alert table (EAT) accordingto an embodiment of the present invention;

FIG. 52 illustrates a method for identifying information related toheader compression, which is included in a payload of a link layerpacket according to an embodiment of the present invention;

FIG. 53 illustrates initialization information according to anembodiment of the present invention;

FIG. 54 illustrates configuration parameters according to an embodimentof the present invention;

FIG. 55 illustrates static chain information according to an embodimentof the present invention;

FIG. 56 illustrates dynamic chain information according to an embodimentof the present invention;

FIG. 57 is a diagram illustrating a header structure of a link layerpacket when an MPEG-2 transport stream (TS) is input to a link layer,according to an embodiment of the present invention;

FIG. 58 is a diagram illustrating the number of MPEG-2 TS packetsincluded in a payload of a link layer packet according to a value of acount field, according to an embodiment of the present invention;

FIG. 59 is a diagram illustrating a header of an MPEG-2 TS packetaccording to an embodiment of the present invention;

FIG. 60 is a diagram illustrating a procedure for changing use of atransport EI field by a transmitter according to an embodiment of thepresent invention;

FIG. 61 is a diagram illustrating a procedure for encapsulating anMPEG-2 TS packet according to an embodiment of the present invention;

FIG. 62 is a diagram illustrating a procedure for encapsulating MPEG-2TS packets having the same PIDs, according to an embodiment of thepresent invention;

FIG. 63 is a diagram illustrating an equation for obtaining a length ofa link layer packet during a common PID reduction procedure and a commonPID reduction procedure, according to an embodiment of the presentinvention;

FIG. 64 is a diagram illustrating the number of concatenated MPEG-2 TSpackets according to a value of a count field and a length of a linklayer packet according to the number when common PID reduction isapplied, according to an embodiment of the present invention;

FIG. 65 is a diagram illustrating a method for encapsulating an MPEG-2TS packet including a null packet, according to an embodiment of thepresent invention;

FIG. 66 is a diagram illustrating a procedure for processing anindicator for counting deleted null packets and an equation forobtaining a length of a link layer packet during the procedure,according to an embodiment of the present invention;

FIG. 67 is a diagram illustrating a procedure for encapsulating anMPEG-2 TS packet including a null packet, according to anotherembodiment of the present invention;

FIG. 68 is a diagram illustrating a procedure for encapsulating MPEG-2TS packets including the same packet identifier (PID) in a streamincluding a null packet, according to an embodiment of the presentinvention;

FIG. 69 is a diagram illustrating an equation for obtaining a length ofa link layer packet while MPEG-2 TS packets including the same packetidentifier (PID) are encapsulated in a stream including a null packet,according to an embodiment of the present invention;

FIG. 70 is a view illustrating a protocol stack for a next generationbroadcasting system according to an embodiment of the present invention;

FIG. 71 is a view illustrating the interface of a link layer accordingto an embodiment of the present invention;

FIG. 72 is a view illustrating an operation diagram of a normal mode,which is one of the operation modes of a link layer according to anembodiment of the present invention;

FIG. 73 is a view illustrating an operation diagram of a transparentmode, which is one of the operation modes of a link layer according toan embodiment of the present invention;

FIG. 74 is a view illustrating the structure of a link layer on atransmitter side according to an embodiment of the present invention(normal mode);

FIG. 75 is a view illustrating the structure of a link layer on areceiver side according to an embodiment of the present invention(normal mode);

FIG. 76 is a view illustrating the definition of a link layer based onthe organization type thereof according to an embodiment of the presentinvention;

FIG. 77 is a view illustrating the processing of a broadcast signal, ina case in which a logical data path includes only a normal data pipe,according to an embodiment of the present invention;

FIG. 78 is a view illustrating the processing of a broadcast signal, ina case in which a logical data path includes a normal data pipe and abase data pipe, according to an embodiment of the present invention;

FIG. 79 is a view illustrating the processing of a broadcast signal, ina case in which a logical data path includes a normal data pipe and adedicated channel, according to an embodiment of the present invention;

FIG. 80 is a view illustrating the processing of a broadcast signal, ina case in which a logical data path includes a normal data pipe, a basedata pipe, and a dedicated channel, according to an embodiment of thepresent invention;

FIG. 81 is a view illustrating a detailed processing operation ofsignals and/or data in a link layer of a receiver, in a case in which alogical data path includes a normal data pipe, a base data pipe, and adedicated channel, according to an embodiment of the present invention;

FIG. 82 is a view illustrating the syntax of a fast information channel(FIC) according to an embodiment of the present invention;

FIG. 83 is a view illustrating the syntax of an emergency alert table(EAT) according to an embodiment of the present invention;

FIG. 84 is a view illustrating a packet that is transmitted through adata pipe according to an embodiment of the present invention;

FIG. 85 is a view illustrating the detailed processing operation ofsignals and/or data in each protocol stack of a transmitter, in a casein which a logical data path of a physical layer includes a dedicatedchannel, a base DP, and a normal data DP, according to anotherembodiment of the present invention;

FIG. 86 is a view illustrating a detailed processing operation ofsignals and/or data in each protocol stack of a receiver, in a case inwhich a logical data path of a physical layer includes a dedicatedchannel, a base DP, and a normal data DP, according to anotherembodiment of the present invention;

FIG. 87 is a view illustrating the syntax of an FIC according to anotherembodiment of the present invention;

FIG. 88 is a view illustrating Signaling_Information_Part( ) accordingto an embodiment of the present invention;

FIG. 89 is a view illustrating a process of controlling an operationmode of a transmitter and/or a receiver in a link layer according to anembodiment of the present invention;

FIG. 90 is a view illustrating the operation in a link layer based onthe value of a flag and the type of packet that is transmitted to aphysical layer according to an embodiment of the present invention;

FIG. 91 is a view illustrating a descriptor for signaling a mode controlparameter according to an embodiment of the present invention;

FIG. 92 is a view illustrating the operation of a transmitter thatcontrols an operation mode according to an embodiment of the presentinvention;

FIG. 93 is a view illustrating the operation of a transmitter thatprocesses a broadcast signal based on an operation mode according to anembodiment of the present invention;

FIG. 94 is a view illustrating information that identifies anencapsulation mode according to an embodiment of the present invention;

FIG. 95 is a view illustrating information that identifies a headercompression mode according to an embodiment of the present invention;

FIG. 96 is a view illustrating information that identifies a packetreconfiguration mode according to an embodiment of the presentinvention;

FIG. 97 is a view illustrating information that identifies a contexttransmission mode according to an embodiment of the present invention;

FIG. 98 is a view illustrating initialization information, in a case inwhich RoHC is applied in a header compression mode, according to anembodiment of the present invention;

FIG. 99 is a view illustrating information that identifies a link layersignaling path configuration according to an embodiment of the presentinvention;

FIG. 100 is a view illustrating information about signaling pathconfiguration in a bit mapping mode according to an embodiment of thepresent invention;

FIG. 101 is a flowchart illustrating a link layer initializationprocedure according to an embodiment of the present invention;

FIG. 102 is a flowchart illustrating a link layer initializationprocedure according to another embodiment of the present invention;

FIG. 103 is a view illustrating a signaling format in a form fortransmitting an initialization parameter according to an embodiment ofthe present invention;

FIG. 104 is a view illustrating a signaling format in a form fortransmitting an initialization parameter according to another embodimentof the present invention;

FIG. 105 is a view illustrating a signaling format in a form fortransmitting an initialization parameter according to a furtherembodiment of the present invention;

FIG. 106 is a view illustrating a receiver according to an embodiment ofthe present invention;

FIG. 107 illustrates a header structure of a link layer packet accordingto another embodiment of the present invention;

FIG. 108 illustrates a header structure of a link layer packet accordingto another embodiment of the present invention;

FIG. 109 illustrates a header structure of a link layer packet accordingto another embodiment of the present invention;

FIG. 110 illustrates a header structure of a link layer packet accordingto another embodiment of the present invention;

FIG. 111 is a diagram for explanation of an overhead reduction processwhen a TS packet is input to a link layer according to an embodiment ofthe present invention;

FIG. 112 is a diagram for explanation of a null packet deletion pointer(NPDP) field and a deleted null packet counter (DNPC) in an overheadreduction process of a TS packet according to another embodiment of thepresent invention;

FIG. 113 is a diagram for explanation of a NPDP field and a DNPC fieldin an overhead reduction process of a TS packet according to anotherembodiment of the present invention;

FIG. 114 illustrates a structure of a link layer packet when a NPDPfield/DNPC field is used according to an embodiment of the presentinvention;

FIG. 115 is a diagram of a structure of a link layer packet when a NPDPfield/DNPC field is used according to another embodiment of the presentinvention;

FIG. 116 illustrates a null packet deletion mechanism according to aNPDP field/DNPC field according to an embodiment of the presentinvention;

FIG. 117 illustrates a null packet deletion mechanism according to aNPDP field/DNPC field according to another embodiment of the presentinvention;

FIG. 118 is a diagram illustrating a packet length indication method ofa link layer packet including a TS packet according to an embodiment ofthe present invention;

FIG. 119 is a diagram illustrating a header structure of a link layerpacket according to another embodiment of the present invention;

FIG. 120 illustrates a header structure of a link layer packet accordingto another embodiment of the present invention;

FIG. 121 is a diagram illustrating a method for configuring a link layeron a protocol stack according to an embodiment of the present invention;

FIG. 122 is a diagram illustrating a method for configuring a link layeron a protocol stack according to another embodiment of the presentinvention;

FIG. 123 is a diagram illustrating a method for configuring a link layeron a protocol stack according to another embodiment of the presentinvention;

FIG. 124 is a diagram illustrating a signaling method for indicating alink layer configuration on a protocol stack according to an embodimentof the present invention;

FIG. 125 is a diagram illustrating a signaling method for indicating alink layer configuration on a protocol stack according to anotherembodiment of the present invention;

FIG. 126 is a diagram illustrating a method for transmitting a broadcastsignal according to an embodiment of the present invention;

FIG. 127 is a diagram illustrating an apparatus for transmitting abroadcast signal according to an embodiment of the present invention;

FIG. 128 is a diagram illustrating a layer structure when a dedicatedchannel is present according to an embodiment of the present invention;

FIG. 129 is a diagram illustrating a layer structure when a dedicatedchannel is present according to another embodiment of the presentinvention;

FIG. 130 is a diagram illustrating a layer structure when a dedicatedchannel is independently present according to an embodiment of thepresent invention;

FIG. 131 is a diagram illustrating a layer structure when a dedicatedchannel is independently present according to another embodiment of thepresent invention;

FIG. 132 is a diagram illustrating a layer structure when a dedicatedchannel transmits specific data according to an embodiment of thepresent invention;

FIG. 133 is a diagram illustrating a format of (or a dedicated format)of data transmitted through a dedicated channel according to anembodiment of the present invention;

FIG. 134 is a diagram illustrating configuration information of adedicated channel for signaling information about a dedicated channelaccording to an embodiment of the present invention;

FIG. 135 is a flowchart illustrating a broadcast signal transmissionprocessing method according to an embodiment of the present invention;and

FIG. 136 is a diagram illustrating a broadcast system according to anembodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. The detailed description, which will be given below withreference to the accompanying drawings, is intended to explain exemplaryembodiments of the present invention, rather than to show the onlyembodiments that can be implemented according to the present invention.The following detailed description includes specific details in order toprovide a thorough understanding of the present invention. However, itwill be apparent to those skilled in the art that the present inventionmay be practiced without such specific details.

Although the terms used in the present invention are selected fromgenerally known and used terms, some of the terms mentioned in thedescription of the present invention have been selected by the applicantat his or her discretion, the detailed meanings of which are describedin relevant parts of the description herein. Furthermore, it is requiredthat the present invention is understood, not simply by the actual termsused but by the meanings of each term lying within.

The present invention provides apparatuses and methods for transmittingand receiving broadcast signals for future broadcast services. Futurebroadcast services according to an embodiment of the present inventioninclude a terrestrial broadcast service, a mobile broadcast service, anultra high definition television (UHDTV) service, etc. The presentinvention may process broadcast signals for the future broadcastservices through non-MIMO (Multiple Input Multiple Output) or MIMOaccording to one embodiment. A non-MIMO scheme according to anembodiment of the present invention may include a MISO (Multiple InputSingle Output) scheme, a SISO (Single Input Single Output) scheme, etc.

FIG. 1 illustrates a receiver protocol stack according to an embodimentof the present invention.

Two schemes may be used in broadcast service delivery through abroadcast network.

In a first scheme, media processing units (MPUs) are transmitted usingan MMT protocol (MMTP) based on MPEG media transport (MMT). In a secondscheme, dynamic adaptive streaming over HTTP (DASH) segments may betransmitted using real time object delivery over unidirectionaltransport (ROUTE) based on MPEG DASH.

Non-timed content including NRT media, EPG data, and other files isdelivered with ROUTE. Signaling may be delivered over MMTP and/or ROUTE,while bootstrap signaling information is provided by the means of theService List Table (SLT).

In hybrid service delivery, MPEG DASH over HTTP/TCP/IP is used on thebroadband side. Media files in ISO Base Media File Format (BMFF) areused as the delivery, media encapsulation and synchronization format forboth broadcast and broadband delivery. Here, hybrid service delivery mayrefer to a case in which one or more program elements are deliveredthrough a broadband path.

Services are delivered using three functional layers. These are thephysical layer, the delivery layer and the service management layer. Thephysical layer provides the mechanism by which signaling, serviceannouncement and IP packet streams are transported over the broadcastphysical layer and/or broadband physical layer. The delivery layerprovides object and object flow transport functionality. It is enabledby the MMTP or the ROUTE protocol, operating on a UDP/IP multicast overthe broadcast physical layer, and enabled by the HTTP protocol on aTCP/IP unicast over the broadband physical layer. The service managementlayer enables any type of service, such as linear TV or HTML5application service, to be carried by the underlying delivery andphysical layers.

In this figure, a protocol stack part on a broadcast side may be dividedinto a part transmitted through the SLT and the MMTP, and a parttransmitted through ROUTE.

The SLT may be encapsulated through UDP and IP layers. Here, the SLTwill be described below. The MMTP may transmit data formatted in an MPUformat defined in MMT, and signaling information according to the MMTP.The data may be encapsulated through the UDP and IP layers. ROUTE maytransmit data formatted in a DASH segment form, signaling information,and non-timed data such as NRT data, etc. The data may be encapsulatedthrough the UDP and IP layers. According to a given embodiment, some orall processing according to the UDP and IP layers may be omitted. Here,the illustrated signaling information may be signaling informationrelated to a service.

The part transmitted through the SLT and the MMTP and the parttransmitted through ROUTE may be processed in the UDP and IP layers, andthen encapsulated again in a data link layer. The link layer will bedescribed below. Broadcast data processed in the link layer may bemulticast as a broadcast signal through processes such asencoding/interleaving, etc. in the physical layer.

In this figure, a protocol stack part on a broadband side may betransmitted through HTTP as described above. Data formatted in a DASHsegment form, signaling information, NRT information, etc. may betransmitted through HTTP. Here, the illustrated signaling informationmay be signaling information related to a service. The data may beprocessed through the TCP layer and the IP layer, and then encapsulatedinto the link layer. According to a given embodiment, some or all of theTCP, the IP, and the link layer may be omitted. Broadband data processedthereafter may be transmitted by unicast in the broadband through aprocess for transmission in the physical layer.

Service can be a collection of media components presented to the user inaggregate; components can be of multiple media types; a Service can beeither continuous or intermittent; a Service can be Real Time orNon-Real Time; Real Time Service can consist of a sequence of TVprograms.

FIG. 2 illustrates a relation between the SLT and SLS according to anembodiment of the present invention.

Service signaling provides service discovery and descriptioninformation, and comprises two functional components: Bootstrapsignaling via the Service List Table (SLT) and the Service LayerSignaling (SLS). These represent the information which is necessary todiscover and acquire user services. The SLT enables the receiver tobuild a basic service list, and bootstrap the discovery of the SLS foreach service.

The SLT can enable very rapid acquisition of basic service information.The SLS enables the receiver to discover and access services and theircontent components. Details of the SLT and SLS will be described below.

As described in the foregoing, the SLT may be transmitted throughUDP/IP. In this instance, according to a given embodiment, datacorresponding to the SLT may be delivered through the most robust schemein this transmission.

The SLT may have access information for accessing SLS delivered by theROUTE protocol. In other words, the SLT may be bootstrapped into SLSaccording to the ROUTE protocol. The SLS is signaling informationpositioned in an upper layer of ROUTE in the above-described protocolstack, and may be delivered through ROUTE/UDP/IP. The SLS may betransmitted through one of LCT sessions included in a ROUTE session. Itis possible to access a service component corresponding to a desiredservice using the SLS.

In addition, the SLT may have access information for accessing an MMTsignaling component delivered by MMTP. In other words, the SLT may bebootstrapped into SLS according to the MMTP. The SLS may be delivered byan MMTP signaling message defined in MMT. It is possible to access astreaming service component (MPU) corresponding to a desired serviceusing the SLS. As described in the foregoing, in the present invention,an NRT service component is delivered through the ROUTE protocol, andthe SLS according to the MMTP may include information for accessing theROUTE protocol. In broadband delivery, the SLS is carried overHTTP(S)/TCP/IP.

FIG. 3 illustrates an SLT according to an embodiment of the presentinvention.

First, a description will be given of a relation among respectivelogical entities of service management, delivery, and a physical layer.

Services may be signaled as being one of two basic types. First type isa linear audio/video or audio-only service that may have an app-basedenhancement. Second type is a service whose presentation and compositionis controlled by a downloaded application that is executed uponacquisition of the service. The latter can be called an “app-based”service.

The rules regarding presence of ROUTE/LCT sessions and/or MMTP sessionsfor carrying the content components of a service may be as follows.

For broadcast delivery of a linear service without app-basedenhancement, the service's content components can be carried by either(but not both): (1) one or more ROUTE/LCT sessions, or (2) one or moreMMTP sessions.

For broadcast delivery of a linear service with app-based enhancement,the service's content components can be carried by: (1) one or moreROUTE/LCT sessions, and (2) zero or more MMTP sessions.

In certain embodiments, use of both MMTP and ROUTE for streaming mediacomponents in the same service may not be allowed.

For broadcast delivery of an app-based service, the service's contentcomponents can be carried by one or more ROUTE/LCT sessions.

Each ROUTE session comprises one or more LCT sessions which carry as awhole, or in part, the content components that make up the service. Instreaming services delivery, an LCT session may carry an individualcomponent of a user service such as an audio, video or closed captionstream. Streaming media is formatted as DASH Segments.

Each MMTP session comprises one or more MMTP packet flows which carryMMT signaling messages or as a whole, or in part, the content component.An MMTP packet flow may carry MMT signaling messages or componentsformatted as MPUs.

For the delivery of NRT User Services or system metadata, an LCT sessioncarries file-based content items. These content files may consist ofcontinuous (time-based) or discrete (non-time-based) media components ofan NRT service, or metadata such as Service Signaling or ESG fragments.Delivery of system metadata such as service signaling or ESG fragmentsmay also be achieved through the signaling message mode of MMTP.

A broadcast stream is the abstraction for an RF channel, which isdefined in terms of a carrier frequency centered within a specifiedbandwidth. It is identified by the pair [geographic area, frequency]. Aphysical layer pipe (PLP) corresponds to a portion of the RF channel.Each PLP has certain modulation and coding parameters. It is identifiedby a PLP identifier (PLPID), which is unique within the broadcast streamit belongs to. Here, PLP can be referred to as DP (data pipe).

Each service is identified by two forms of service identifier: a compactform that is used in the SLT and is unique only within the broadcastarea; and a globally unique form that is used in the SLS and the ESG. AROUTE session is identified by a source IP address, destination IPaddress and destination port number. An LCT session (associated with theservice component(s) it carries) is identified by a transport sessionidentifier (TSI) which is unique within the scope of the parent ROUTEsession. Properties common to the LCT sessions, and certain propertiesunique to individual LCT sessions, are given in a ROUTE signalingstructure called a service-based transport session instance description(S-TSID), which is part of the service layer signaling. Each LCT sessionis carried over a single physical layer pipe. According to a givenembodiment, one LCT session may be transmitted through a plurality ofPLPs. Different LCT sessions of a ROUTE session may or may not becontained in different physical layer pipes. Here, the ROUTE session maybe delivered through a plurality of PLPs. The properties described inthe S-TSID include the TSI value and PLPID for each LCT session,descriptors for the delivery objects/files, and application layer FECparameters.

A MMTP session is identified by destination IP address and destinationport number. An MMTP packet flow (associated with the servicecomponent(s) it carries) is identified by a packet_id which is uniquewithin the scope of the parent MMTP session. Properties common to eachMMTP packet flow, and certain properties of MMTP packet flows, are givenin the SLT. Properties for each MMTP session are given by MMT signalingmessages, which may be carried within the MMTP session. Different MMTPpacket flows of a MMTP session may or may not be contained in differentphysical layer pipes. Here, the MMTP session may be delivered through aplurality of PLPs. The properties described in the MMT signalingmessages include the packet_id value and PLPID for each MMTP packetflow. Here, the MMT signaling messages may have a form defined in MMT,or have a deformed form according to embodiments to be described below.

Hereinafter, a description will be given of low level signaling (LLS).

Signaling information which is carried in the payload of IP packets witha well-known address/port dedicated to this function is referred to aslow level signaling (LLS). The IP address and the port number may bedifferently configured depending on embodiments. In one embodiment, LLScan be transported in IP packets with address 224.0.23.60 anddestination port 4937/udp. LLS may be positioned in a portion expressedby “SLT” on the above-described protocol stack. However, according to agiven embodiment, the LLS may be transmitted through a separate physicalchannel (dedicated channel) in a signal frame without being subjected toprocessing of the UDP/IP layer.

UDP/IP packets that deliver LLS data may be formatted in a form referredto as an LLS table. A first byte of each UDP/IP packet that delivers theLLS data may correspond to a start of the LLS table. The maximum lengthof any LLS table is limited by the largest IP packet that can bedelivered from the PHY layer, 65,507 bytes.

The LLS table may include an LLS table ID field that identifies a typeof the LLS table, and an LLS table version field that identifies aversion of the LLS table. According to a value indicated by the LLStable ID field, the LLS table may include the above-described SLT or arating region table (RRT). The RRT may have information about contentadvisory rating.

Hereinafter, the SLT will be described. LLS can be signaling informationwhich supports rapid channel scans and bootstrapping of serviceacquisition by the receiver, and SLT can be a table of signalinginformation which is used to build a basic service listing and providebootstrap discovery of SLS.

The function of the SLT is similar to that of the program associationtable (PAT) in MPEG-2 Systems, and the fast information channel (FIC)found in ATSC Systems. For a receiver first encountering the broadcastemission, this is the place to start. SLT supports a rapid channel scanwhich allows a receiver to build a list of all the services it canreceive, with their channel name, channel number, etc., and SLT providesbootstrap information that allows a receiver to discover the SLS foreach service. For ROUTE/DASH-delivered services, the bootstrapinformation includes the destination IP address and destination port ofthe LCT session that carries the SLS. For MMT/MPU-delivered services,the bootstrap information includes the destination IP address anddestination port of the MMTP session carrying the SLS.

The SLT supports rapid channel scans and service acquisition byincluding the following information about each service in the broadcaststream. First, the SLT can include information necessary to allow thepresentation of a service list that is meaningful to viewers and thatcan support initial service selection via channel number or up/downselection. Second, the SLT can include information necessary to locatethe service layer signaling for each service listed. That is, the SLTmay include access information related to a location at which the SLS isdelivered.

The illustrated SLT according to the present embodiment is expressed asan XML document having an SLT root element. According to a givenembodiment, the SLT may be expressed in a binary format or an XMLdocument.

The SLT root element of the SLT illustrated in the figure may include@bsid, @sltSectionVersion, @sltSectionNumber, @totalSltSectionNumbers,@language, @capabilities, InetSigLoc and/or Service. According to agiven embodiment, the SLT root element may further include @providerId.According to a given embodiment, the SLT root element may not include@language.

The service element may include @serviceId, @SLTserviceSeqNumber,@protected, @majorChannelNo, @minorChannelNo, @serviceCategory,@shortServiceName, @hidden, @slsProtocolType, BroadcastSignaling,@slsPlpId, @slsDestinationIpAddress, @slsDestinationUdpPort,@slsSourceIpAddress, @slsMajorProtocolVersion, @slsMinorProtocolVersion,@serviceLanguage, @broadbandAccessRequired, @capabilities and/orInetSigLoc.

According to a given embodiment, an attribute or an element of the SLTmay be added/changed/deleted. Each element included in the SLT mayadditionally have a separate attribute or element, and some attribute orelements according to the present embodiment may be omitted. Here, afield which is marked with @ may correspond to an attribute, and a fieldwhich is not marked with @ may correspond to an element.

@bsid is an identifier of the whole broadcast stream. The value of BSIDmay be unique on a regional level.

@providerId can be an index of broadcaster that is using part or all ofthis broadcast stream. This is an optional attribute. When it's notpresent, it means that this broadcast stream is being used by onebroadcaster. @providerId is not illustrated in the figure.

@sltSectionVersion can be a version number of the SLT section. ThesltSectionVersion can be incremented by 1 when a change in theinformation carried within the slt occurs. When it reaches maximumvalue, it wraps around to 0.

@sltSectionNumber can be the number, counting from 1, of this section ofthe SLT. In other words, @sltSectionNumber may correspond to a sectionnumber of the SLT section. When this field is not used,@sltSectionNumber may be set to a default value of 1.

@totalSltSectionNumbers can be the total number of sections (that is,the section with the highest sltSectionNumber) of the SLT of which thissection is part. sltSectionNumber and totalSltSectionNumbers togethercan be considered to indicate “Part M of N” of one portion of the SLTwhen it is sent in fragments. In other words, when the SLT istransmitted, transmission through fragmentation may be supported. Whenthis field is not used, @totalSltSectionNumbers may be set to a defaultvalue of 1. A case in which this field is not used may correspond to acase in which the SLT is not transmitted by being fragmented.

@language can indicate primary language of the services included in thisslt instance. According to a given embodiment, a value of this field mayhave be a three-character language code defined in the ISO. This fieldmay be omitted.

@capabilities can indicate required capabilities for decoding andmeaningfully presenting the content for all the services in this sltinstance.

InetSigLoc can provide a URL telling the receiver where it can acquireany requested type of data from external server(s) via broadband. Thiselement may include @urlType as a lower field. According to a value ofthe @urlType field, a type of a URL provided by InetSigLoc may beindicated. According to a given embodiment, when the @urlType field hasa value of 0, InetSigLoc may provide a URL of a signaling server. Whenthe @urlType field has a value of 1, InetSigLoc may provide a URL of anESG server. When the @urlType field has other values, the field may bereserved for future use.

The service field is an element having information about each service,and may correspond to a service entry. Service element fieldscorresponding to the number of services indicated by the SLT may bepresent. Hereinafter, a description will be given of a lowerattribute/element of the service field.

@serviceId can be an integer number that uniquely identify this servicewithin the scope of this broadcast area. According to a givenembodiment, a scope of @serviceId may be changed. SLTserviceSeqNumbercan be an integer number that indicates the sequence number of the SLTservice information with service ID equal to the serviceId attributeabove. SLTserviceSeqNumber value can start at 0 for each service and canbe incremented by 1 every time any attribute in this service element ischanged. If no attribute values are changed compared to the previousService element with a particular value of ServiceID thenSLTserviceSeqNumber would not be incremented. The SLTserviceSeqNumberfield wraps back to 0 after reaching the maximum value.

@protected is flag information which may indicate whether one or morecomponents for significant reproduction of the service are in aprotected state. When set to “1” (true), that one or more componentsnecessary for meaningful presentation is protected. When set to “0”(false), this flag indicates that no components necessary for meaningfulpresentation of the service are protected. Default value is false.

@majorChannelNo is an integer number representing the “major” channelnumber of the service. An example of the field may have a range of 1 to999.

@minorChannelNo is an integer number representing the “minor” channelnumber of the service. An example of the field may have a range of 1 to999.

@serviceCategory can indicate the category of this service. This fieldmay indicate a type that varies depending on embodiments. According to agiven embodiment, when this field has values of 1, 2, and 3, the valuesmay correspond to a linear A/V service, a linear audio only service, andan app-based service, respectively. When this field has a value of 0,the value may correspond to a service of an undefined category. Whenthis field has other values except for 1, 2, and 3, the field may bereserved for future use. @shortServiceName can be a short string name ofthe Service.

@hidden can be boolean value that when present and set to “true”indicates that the service is intended for testing or proprietary use,and is not to be selected by ordinary TV receivers. The default value is“false” when not present.

@slsProtocolType can be an attribute indicating the type of protocol ofService Layer Signaling used by this service. This field may indicate atype that varies depending on embodiments. According to a givenembodiment, when this field has values of 1 and 2, protocols of SLS usedby respective corresponding services may be ROUTE and MMTP,respectively. When this field has other values except for 0, the fieldmay be reserved for future use. This field may be referred to as@slsProtocol.

BroadcastSignaling and lower attributes/elements thereof may provideinformation related to broadcast signaling. When the BroadcastSignalingelement is not present, the child element InetSigLoc of the parentservice element can be present and its attribute urlType includesURL_type 0x00 (URL to signaling server). In this case attribute urlsupports the query parameter svc=<service_id> where service_idcorresponds to the serviceId attribute for the parent service element.

Alternatively when the BroadcastSignaling element is not present, theelement InetSigLoc can be present as a child element of the slt rootelement and the attribute urlType of that InetSigLoc element includesURL_type 0x00 (URL to signaling server). In this case, attribute url forURL_type 0x00 supports the query parameter svc=<service_id> whereservice_id corresponds to the serviceId attribute for the parent Serviceelement.

@slsPlpId can be a string representing an integer number indicating thePLP ID of the physical layer pipe carrying the SLS for this service.

@slsDestinationIpAddress can be a string containing the dotted-IPv4destination address of the packets carrying SLS data for this service.

@slsDestinationUdpPort can be a string containing the port number of thepackets carrying SLS data for this service. As described in theforegoing, SLS bootstrapping may be performed by destination IP/UDPinformation.

@slsSourceIpAddress can be a string containing the dotted-IPv4 sourceaddress of the packets carrying SLS data for this service.

@slsMajorProtocolVersion can be major version number of the protocolused to deliver the service layer signaling for this service. Defaultvalue is 1.

@SlsMinorProtocolVersion can be minor version number of the protocolused to deliver the service layer signaling for this service. Defaultvalue is 0.

@serviceLanguage can be a three-character language code indicating theprimary language of the service. A value of this field may have a formthat varies depending on embodiments.

@broadbandAccessRequired can be a Boolean indicating that broadbandaccess is required for a receiver to make a meaningful presentation ofthe service. Default value is false. When this field has a value ofTrue, the receiver needs to access a broadband for significant servicereproduction, which may correspond to a case of hybrid service delivery.

@capabilities can represent required capabilities for decoding andmeaningfully presenting the content for the service with service IDequal to the service Id attribute above.

InetSigLoc can provide a URL for access to signaling or announcementinformation via broadband, if available. Its data type can be anextension of the any URL data type, adding an @urlType attribute thatindicates what the URL gives access to. An @urlType field of this fieldmay indicate the same meaning as that of the @urlType field ofInetSigLoc described above. When an InetSigLoc element of attributeURL_type 0x00 is present as an element of the SLT, it can be used tomake HTTP requests for signaling metadata. The HTTP POST message bodymay include a service term. When the InetSigLoc element appears at thesection level, the service term is used to indicate the service to whichthe requested signaling metadata objects apply. If the service term isnot present, then the signaling metadata objects for all services in thesection are requested. When the InetSigLoc appears at the service level,then no service term is needed to designate the desired service. When anInetSigLoc element of attribute URL_type 0x01 is provided, it can beused to retrieve ESG data via broadband. If the element appears as achild element of the service element, then the URL can be used toretrieve ESG data for that service. If the element appears as a childelement of the SLT element, then the URL can be used to retrieve ESGdata for all services in that section.

In another example of the SLT, @sltSectionVersion, @sltSectionNumber,@totalSltSectionNumbers and/or @language fields of the SLT may beomitted.

In addition, the above-described InetSigLoc field may be replaced by@sltInetSigUri and/or @sltInetEsgUri field. The two fields may includethe URI of the signaling server and URI information of the ESG server,respectively. The InetSigLoc field corresponding to a lower field of theSLT and the InetSigLoc field corresponding to a lower field of theservice field may be replaced in a similar manner.

The suggested default values may vary depending on embodiments. Anillustrated “use” column relates to the respective fields. Here, “1” mayindicate that a corresponding field is an essential field, and “0 . . .1” may indicate that a corresponding field is an optional field.

FIG. 4 illustrates SLS bootstrapping and a service discovery processaccording to an embodiment of the present invention.

Hereinafter, SLS will be described.

SLS can be signaling which provides information for discovery andacquisition of services and their content components.

For ROUTE/DASH, the SLS for each service describes characteristics ofthe service, such as a list of its components and where to acquire them,and the receiver capabilities required to make a meaningful presentationof the service. In the ROUTE/DASH system, the SLS includes the userservice bundle description (USBD), the S-TSID and the DASH mediapresentation description (MPD). Here, USBD or user service description(USD) is one of SLS XML fragments, and may function as a signaling herbthat describes specific descriptive information. USBD/USD may beextended beyond 3GPP MBMS. Details of USBD/USD will be described below.

The service signaling focuses on basic attributes of the service itself,especially those attributes needed to acquire the service. Properties ofthe service and programming that are intended for viewers appear asservice announcement, or ESG data.

Having separate Service Signaling for each service permits a receiver toacquire the appropriate SLS for a service of interest without the needto parse the entire SLS carried within a broadcast stream.

For optional broadband delivery of Service Signaling, the SLT caninclude HTTP URLs where the Service Signaling files can be obtained, asdescribed above.

LLS is used for bootstrapping SLS acquisition, and subsequently, the SLSis used to acquire service components delivered on either ROUTE sessionsor MMTP sessions. The described figure illustrates the followingsignaling sequences. Receiver starts acquiring the SLT described above.Each service identified by service id delivered over ROUTE sessionsprovides SLS bootstrapping information: PLPID(#1), source IP address(sIP1), destination IP address (dIP1), and destination port number(dPort1). Each service identified by service_id delivered over MMTPsessions provides SLS bootstrapping information: PLPID(#2), destinationIP address (dIP2), and destination port number (dPort2).

For streaming services delivery using ROUTE, the receiver can acquireSLS fragments carried over the IP/UDP/LCT session and PLP; whereas forstreaming services delivery using MMTP, the receiver can acquire SLSfragments carried over an MMTP session and PLP. For service deliveryusing ROUTE, these SLS fragments include USBD/USD fragments, S-TSIDfragments, and MPD fragments. They are relevant to one service. USBD/USDfragments describe service layer properties and provide URI referencesto S-TSID fragments and URI references to MPD fragments. In other words,the USBD/USD may refer to S-TSID and MPD. For service delivery usingMMTP, the USBD references the MMT signaling's MPT message, the MP Tableof which provides identification of package ID and location informationfor assets belonging to the service. Here, an asset is a multimedia dataentity, and may refer to a data entity which is combined into one uniqueID and is used to generate one multimedia presentation. The asset maycorrespond to a service component included in one service. The MPTmessage is a message having the MP table of MMT. Here, the MP table maybe an MMT package table having information about content and an MMTasset. Details may be similar to a definition in MMT. Here, mediapresentation may correspond to a collection of data that establishesbounded/unbounded presentation of media content.

The S-TSID fragment provides component acquisition informationassociated with one service and mapping between DASH Representationsfound in the MPD and in the TSI corresponding to the component of theservice. The S-TSID can provide component acquisition information in theform of a TSI and the associated DASH representation identifier, andPLPID carrying DASH segments associated with the DASH representation. Bythe PLPID and TSI values, the receiver collects the audio/videocomponents from the service and begins buffering DASH media segmentsthen applies the appropriate decoding processes.

For USBD listing service components delivered on MMTP sessions, asillustrated by “Service #2” in the described figure, the receiver alsoacquires an MPT message with matching MMTpackage_id to complete the SLS.An MPT message provides the full list of service components comprising aservice and the acquisition information for each component. Componentacquisition information includes MMTP session information, the PLPIDcarrying the session and the packet_id within that session.

According to a given embodiment, for example, in ROUTE, two or moreS-TSID fragments may be used. Each fragment may provide accessinformation related to LCT sessions delivering content of each service.

In ROUTE, S-TSID, USBD/USD, MPD, or an LCT session delivering S-TSID,USBD/USD or MPD may be referred to as a service signaling channel. InMMTP, USBD/UD, an MMT signaling message, or a packet flow delivering theMMTP or USBD/UD may be referred to as a service signaling channel.

Unlike the illustrated example, one ROUTE or MMTP session may bedelivered through a plurality of PLPs. In other words, one service maybe delivered through one or more PLPs. As described in the foregoing,one LCT session may be delivered through one PLP. Unlike the figure,according to a given embodiment, components included in one service maybe delivered through different ROUTE sessions. In addition, according toa given embodiment, components included in one service may be deliveredthrough different MMTP sessions. According to a given embodiment,components included in one service may be delivered separately through aROUTE session and an MMTP session. Although not illustrated, componentsincluded in one service may be delivered via broadband (hybriddelivery).

FIG. 5 illustrates a USBD fragment for ROUTE/DASH according to anembodiment of the present invention.

Hereinafter, a description will be given of SLS in delivery based onROUTE.

SLS provides detailed technical information to the receiver to enablethe discovery and access of services and their content components. Itcan include a set of XML-encoded metadata fragments carried over adedicated LCT session. That LCT session can be acquired using thebootstrap information contained in the SLT as described above. The SLSis defined on a per-service level, and it describes the characteristicsand access information of the service, such as a list of its contentcomponents and how to acquire them, and the receiver capabilitiesrequired to make a meaningful presentation of the service. In theROUTE/DASH system, for linear services delivery, the SLS consists of thefollowing metadata fragments: USBD, S-TSID and the DASH MPD. The SLSfragments can be delivered on a dedicated LCT transport session withTSI=0. According to a given embodiment, a TSI of a particular LCTsession (dedicated LCT session) in which an SLS fragment is deliveredmay have a different value. According to a given embodiment, an LCTsession in which an SLS fragment is delivered may be signaled using theSLT or another scheme.

ROUTE/DASH SLS can include the user service bundle description (USBD)and service-based transport session instance description (S-TSID)metadata fragments. These service signaling fragments are applicable toboth linear and application-based services. The USBD fragment containsservice identification, device capabilities information, references toother SLS fragments required to access the service and constituent mediacomponents, and metadata to enable the receiver to determine thetransport mode (broadcast and/or broadband) of service components. TheS-TSID fragment, referenced by the USBD, provides transport sessiondescriptions for the one or more ROUTE/LCT sessions in which the mediacontent components of a service are delivered, and descriptions of thedelivery objects carried in those LCT sessions. The USBD and S-TSID willbe described below.

In streaming content signaling in ROUTE-based delivery, a streamingcontent signaling component of SLS corresponds to an MPD fragment. TheMPD is typically associated with linear services for the delivery ofDASH Segments as streaming content. The MPD provides the resourceidentifiers for individual media components of the linear/streamingservice in the form of Segment URLs, and the context of the identifiedresources within the Media Presentation. Details of the MPD will bedescribed below.

In app-based enhancement signaling in ROUTE-based delivery, app-basedenhancement signaling pertains to the delivery of app-based enhancementcomponents, such as an application logic file, locally-cached mediafiles, an network content items, or a notification stream. Anapplication can also retrieve locally-cached data over a broadbandconnection when available.

Hereinafter, a description will be given of details of USBD/USDillustrated in the figure.

The top level or entry point SLS fragment is the USBD fragment. Anillustrated USBD fragment is an example of the present invention, basicfields of the USBD fragment not illustrated in the figure may beadditionally provided according to a given embodiment. As described inthe foregoing, the illustrated USBD fragment has an extended form, andmay have fields added to a basic configuration.

The illustrated USBD may have a bundleDescription root element. ThebundleDescription root element may have a userServiceDescriptionelement. The userServiceDescription element may correspond to aninstance for one service.

The userServiceDescription element may include @serviceId,@atsc:serviceId, @atsc:serviceStatus, @atsc:fullMPDUri, @atsc:sTSIDUri,name, serviceLanguage, atsc:capabilityCode and/or deliveryMethod.

@serviceId can be a globally unique URI that identifies a service,unique within the scope of the BSID. This parameter can be used to linkto ESG data (Service@globalServiceID).

@atsc:serviceId is a reference to corresponding service entry inLLS(SLT). The value of this attribute is the same value of serviceIdassigned to the entry.

@atsc:serviceStatus can specify the status of this service. The valueindicates whether this service is active or inactive. When set to “1”(true), that indicates service is active. When this field is not used,@atsc:serviceStatus may be set to a default value of 1.

@atsc:fullMPDUri can reference an MPD fragment which containsdescriptions for contents components of the service delivered overbroadcast and optionally, also over broadband.

@atsc:sTSIDUri can reference the S-TSID fragment which provides accessrelated parameters to the Transport sessions carrying contents of thisservice.

name can indicate name of the service as given by the lang attribute.name element can include lang attribute, which indicating language ofthe service name. The language can be specified according to XML datatypes.

serviceLanguage can represent available languages of the service. Thelanguage can be specified according to XML data types.

atsc:capabilityCode can specify the capabilities required in thereceiver to be able to create a meaningful presentation of the contentof this service. According to a given embodiment, this field may specifya predefined capability group. Here, the capability group may be a groupof capability attribute values for significant presentation. This fieldmay be omitted according to a given embodiment.

deliveryMethod can be a container of transport related informationpertaining to the contents of the service over broadcast and(optionally) broadband modes of access. Referring to data included inthe service, when the number of the data is N, delivery schemes forrespective data may be described by this element. The deliveryMethod mayinclude an r12:broadcastAppService element and an r12:unicastAppServiceelement. Each lower element may include a basePattern element as a lowerelement.

r12:broadcastAppService can be a DASH Representation delivered overbroadcast, in multiplexed or non-multiplexed form, containing thecorresponding media component(s) belonging to the service, across allPeriods of the affiliated media presentation. In other words, each ofthe fields may indicate DASH representation delivered through thebroadcast network.

r12:unicastAppService can be a DASH Representation delivered overbroadband, in multiplexed or non-multiplexed form, containing theconstituent media content component(s) belonging to the service, acrossall periods of the affiliated media presentation. In other words, eachof the fields may indicate DASH representation delivered via broadband.

basePattern can be a character pattern for use by the receiver to matchagainst any portion of the segment URL used by the DASH client torequest media segments of a parent representation under its containingperiod. A match implies that the corresponding requested media segmentis carried over broadcast transport. In a URL address for receiving DASHrepresentation expressed by each of the r12:broadcastAppService elementand the r12:unicastAppService element, a part of the URL, etc. may havea particular pattern. The pattern may be described by this field. Somedata may be distinguished using this information. The proposed defaultvalues may vary depending on embodiments. The “use” column illustratedin the figure relates to each field. Here, M may denote an essentialfield, 0 may denote an optional field, OD may denote an optional fieldhaving a default value, and CM may denote a conditional essential field.0 . . . 1 to 0 . . . N may indicate the number of available fields.

FIG. 6 illustrates an S-TSID fragment for ROUTE/DASH according to anembodiment of the present invention.

Hereinafter, a description will be given of the S-TSID illustrated inthe figure in detail.

S-TSID can be an SLS XML fragment which provides the overall sessiondescription information for transport session(s) which carry the contentcomponents of a service. The S-TSID is the SLS metadata fragment thatcontains the overall transport session description information for thezero or more ROUTE sessions and constituent LCT sessions in which themedia content components of a service are delivered. The S-TSID alsoincludes file metadata for the delivery object or object flow carried inthe LCT sessions of the service, as well as additional information onthe payload formats and content components carried in those LCTsessions.

Each instance of the S-TSID fragment is referenced in the USBD fragmentby the @atsc:sTSIDUri attribute of the userServiceDescription element.The illustrated S-TSID according to the present embodiment is expressedas an XML document. According to a given embodiment, the S-TSID may beexpressed in a binary format or as an XML document.

The illustrated S-TSID may have an S-TSID root element. The S-TSID rootelement may include @serviceId and/or RS.

@serviceID can be a reference corresponding service element in the USD.The value of this attribute can reference a service with a correspondingvalue of service_id.

The RS element may have information about a ROUTE session for deliveringthe service data. Service data or service components may be deliveredthrough a plurality of ROUTE sessions, and thus the number of RSelements may be 1 to N.

The RS element may include @bsid, @sIpAddr, @dIpAddr, @dport, @PLPIDand/or LS.

@bsid can be an identifier of the broadcast stream within which thecontent component(s) of the broadcastAppService are carried. When thisattribute is absent, the default broadcast stream is the one whose PLPscarry SLS fragments for this service. Its value can be identical to thatof the broadcast stream id in the SLT.

@sIpAddr can indicate source IP address. Here, the source IP address maybe a source IP address of a ROUTE session for delivering a servicecomponent included in the service. As described in the foregoing,service components of one service may be delivered through a pluralityof ROUTE sessions. Thus, the service components may be transmitted usinganother ROUTE session other than the ROUTE session for delivering theS-TSID. Therefore, this field may be used to indicate the source IPaddress of the ROUTE session. A default value of this field may be asource IP address of a current ROUTE session. When a service componentis delivered through another ROUTE session, and thus the ROUTE sessionneeds to be indicated, a value of this field may be a value of a sourceIP address of the ROUTE session. In this case, this field may correspondto M, that is, an essential field.

@dIpAddr can indicate destination IP address. Here, a destination IPaddress may be a destination IP address of a ROUTE session that deliversa service component included in a service. For a similar case to theabove description of @sIpAddr, this field may indicate a destination IPaddress of a ROUTE session that delivers a service component. A defaultvalue of this field may be a destination IP address of a current ROUTEsession. When a service component is delivered through another ROUTEsession, and thus the ROUTE session needs to be indicated, a value ofthis field may be a value of a destination IP address of the ROUTEsession. In this case, this field may correspond to M, that is, anessential field.

@dport can indicate destination port. Here, a destination port may be adestination port of a ROUTE session that delivers a service componentincluded in a service. For a similar case to the above description of@sIpAddr, this field may indicate a destination port of a ROUTE sessionthat delivers a service component. A default value of this field may bea destination port number of a current ROUTE session. When a servicecomponent is delivered through another ROUTE session, and thus the ROUTEsession needs to be indicated, a value of this field may be adestination port number value of the ROUTE session. In this case, thisfield may correspond to M, that is, an essential field.

@PLPID may be an ID of a PLP for a ROUTE session expressed by an RS. Adefault value may be an ID of a PLP of an LCT session including acurrent S-TSID. According to a given embodiment, this field may have anID value of a PLP for an LCT session for delivering an S-TSID in theROUTE session, and may have ID values of all PLPs for the ROUTE session.

An LS element may have information about an LCT session for delivering aservice data. Service data or service components may be deliveredthrough a plurality of LCT sessions, and thus the number of LS elementsmay be 1 to N.

The LS element may include @tsi, @PLPID, @bw, @startTime, @endTime,SrcFlow and/or RprFlow.

@tsi may indicate a TSI value of an LCT session for delivering a servicecomponent of a service.

@PLPID may have ID information of a PLP for the LCT session. This valuemay be overwritten on a basic ROUTE session value.

@bw may indicate a maximum bandwidth value. @startTime may indicate astart time of the LCT session. @endTime may indicate an end time of theLCT session. A SrcFlow element may describe a source flow of ROUTE. AnRprFlow element may describe a repair flow of ROUTE.

The proposed default values may be varied according to an embodiment.The “use” column illustrated in the figure relates to each field. Here,M may denote an essential field, O may denote an optional field, OD maydenote an optional field having a default value, and CM may denote aconditional essential field. 0 . . . 1 to 0 . . . N may indicate thenumber of available fields.

Hereinafter, a description will be given of MPD for ROUTE/DASH.

The MPD is an SLS metadata fragment which contains a formalizeddescription of a DASH Media Presentation, corresponding to a linearservice of a given duration defined by the broadcaster (for example asingle TV program, or the set of contiguous linear TV programs over aperiod of time). The contents of the MPD provide the resourceidentifiers for Segments and the context for the identified resourceswithin the Media Presentation. The data structure and semantics of theMPD fragment can be according to the MPD defined by MPEG DASH.

One or more of the DASH Representations conveyed in the MPD can becarried over broadcast. The MPD may describe additional Representationsdelivered over broadband, e.g. in the case of a hybrid service, or tosupport service continuity in handoff from broadcast to broadcast due tobroadcast signal degradation (e.g. driving through a tunnel).

FIG. 7 illustrates a USBD/USD fragment for MMT according to anembodiment of the present invention.

MMT SLS for linear services comprises the USBD fragment and the MMTPackage (MP) table. The MP table is as described above. The USBDfragment contains service identification, device capabilitiesinformation, references to other SLS information required to access theservice and constituent media components, and the metadata to enable thereceiver to determine the transport mode (broadcast and/or broadband) ofthe service components. The MP table for MPU components, referenced bythe USBD, provides transport session descriptions for the MMTP sessionsin which the media content components of a service are delivered and thedescriptions of the Assets carried in those MMTP sessions.

The streaming content signaling component of the SLS for MPU componentscorresponds to the MP table defined in MMT. The MP table provides a listof MMT assets where each asset corresponds to a single service componentand the description of the location information for this component.

USBD fragments may also contain references to the S-TSID and the MPD asdescribed above, for service components delivered by the ROUTE protocoland the broadband, respectively. According to a given embodiment, indelivery through MMT, a service component delivered through the ROUTEprotocol is NRT data, etc. Thus, in this case, MPD may be unnecessary.In addition, in delivery through MMT, information about an LCT sessionfor delivering a service component, which is delivered via broadband, isunnecessary, and thus an S-TSID may be unnecessary. Here, an MMT packagemay be a logical collection of media data delivered using MMT. Here, anMMTP packet may refer to a formatted unit of media data delivered usingMMT. An MPU may refer to a generic container of independently decodabletimed/non-timed data. Here, data in the MPU is media codec agnostic.

Hereinafter, a description will be given of details of the USBD/USDillustrated in the figure.

The illustrated USBD fragment is an example of the present invention,and basic fields of the USBD fragment may be additionally providedaccording to an embodiment. As described in the foregoing, theillustrated USBD fragment has an extended form, and may have fieldsadded to a basic structure.

The illustrated USBD according to an embodiment of the present inventionis expressed as an XML document. According to a given embodiment, theUSBD may be expressed in a binary format or as an XML document.

The illustrated USBD may have a bundleDescription root element. ThebundleDescription root element may have a userServiceDescriptionelement. The userServiceDescription element may be an instance for oneservice.

The userServiceDescription element may include @serviceId,@atsc:serviceId, name, serviceLanguage, atsc:capabilityCode,atsc:Channel, atsc:mpuComponent, atsc:routeComponent,atsc:broadbandComponent and/or atsc:ComponentInfo.

Here, @serviceId, @atsc:serviceId, name, serviceLanguage, andatsc:capabilityCode may be as described above. The lang field below thename field may be as described above. atsc:capabilityCode may be omittedaccording to a given embodiment.

The userServiceDescription element may further include anatsc:contentAdvisoryRating element according to an embodiment. Thiselement may be an optional element. atsc:contentAdvisoryRating canspecify the content advisory rating. This field is not illustrated inthe figure.

atsc:Channel may have information about a channel of a service. Theatsc:Channel element may include @atsc:majorChannelNo,@atsc:minorChannelNo, @atsc:serviceLang, @atsc:serviceGenre,@atsc:serviceIcon and/or atsc:ServiceDescription. @atsc:majorChannelNo,@atsc:minorChannelNo, and @atsc:serviceLang may be omitted according toa given embodiment.

@atsc:majorChannelNo is an attribute that indicates the major channelnumber of the service.

@atsc:minorChannelNo is an attribute that indicates the minor channelnumber of the service.

@atsc:serviceLang is an attribute that indicates the primary languageused in the service.

@atsc:serviceGenre is an attribute that indicates primary genre of theservice.

@atsc:serviceIcon is an attribute that indicates the Uniform ResourceLocator (URL) for the icon used to represent this service.

atsc:ServiceDescription includes service description, possibly inmultiple languages. atsc:ServiceDescription includes can include@atsc:serviceDescrText and/or @atsc:serviceDescrLang.

@atsc:serviceDescrText is an attribute that indicates description of theservice.

@atsc:serviceDescrLang is an attribute that indicates the language ofthe serviceDescrText attribute above.

atsc:mpuComponent may have information about a content component of aservice delivered in a form of an MPU. atsc:mpuComponent may include@atsc:mmtPackageId and/or @atsc:nextMmtPackageId.

@atsc:mmtPackageId can reference a MMT Package for content components ofthe service delivered as MPUs.

@atsc:nextMmtPackageId can reference a MMT Package to be used after theone referenced by @atsc:mmtPackageId in time for content components ofthe service delivered as MPUs.

atsc:routeComponent may have information about a content component of aservice delivered through ROUTE. atsc:routeComponent may include@atsc:sTSIDUri, @sTSIDPlpId, @sTSIDDestinationIpAddress,@sTSIDDestinationUdpPort, @sTSIDSourceIpAddress,@sTSIDMajorProtocolVersion and/or @sTSIDMinorProtocolVersion.

@atsc:sTSIDUri can be a reference to the S-TSID fragment which providesaccess related parameters to the Transport sessions carrying contents ofthis service. This field may be the same as a URI for referring to anS-TSID in USBD for ROUTE described above. As described in the foregoing,in service delivery by the MMTP, service components, which are deliveredthrough NRT, etc., may be delivered by ROUTE. This field may be used torefer to the S-TSID therefor.

@sTSIDPlpId can be a string representing an integer number indicatingthe PLP ID of the physical layer pipe carrying the S-TSID for thisservice. (default: current physical layer pipe).

@sTSIDDestinationIpAddress can be a string containing the dotted-IPv4destination address of the packets carrying S-TSID for this service.(default: current MMTP session's source IP address).

@sTSIDDestinationUdpPort can be a string containing the port number ofthe packets carrying S-TSID for this service.

@sTSIDSourceIpAddress can be a string containing the dotted-IPv4 sourceaddress of the packets carrying S-TSID for this service.

@sTSIDMajorProtocolVersion can indicate major version number of theprotocol used to deliver the S-TSID for this service. Default value is1.

@sTSIDMinorProtocolVersion can indicate minor version number of theprotocol used to deliver the S-TSID for this service. Default value is0.

atsc:broadbandComponent may have information about a content componentof a service delivered via broadband. In other words,atsc:broadbandComponent may be a field on the assumption of hybriddelivery. atsc:broadbandComponent may further include @atsc:fullfMPDUri.

@atsc:fullfMPDUri can be a reference to an MPD fragment which containsdescriptions for contents components of the service delivered overbroadband.

An atsc:ComponentInfo field may have information about an availablecomponent of a service. The atsc:ComponentInfo field may haveinformation about a type, a role, a name, etc. of each component. Thenumber of atsc:ComponentInfo fields may correspond to the number (N) ofrespective components. The atsc:ComponentInfo field may include@atsc:componentType, @atsc:componentRole, @batsc:componentProtectedFlag,@atsc:componentId and/or atsc:componentName.

@atsc:componentType is an attribute that indicates the type of thiscomponent. Value of 0 indicates an audio component. Value of 1 indicatesa video component. Value of 2 indicated a closed caption component.Value of 3 indicates an application component. Values 4 to 7 arereserved. A meaning of a value of this field may be differently setdepending on embodiments.

@atsc:componentRole is an attribute that indicates the role or kind ofthis component.

For audio (when componentType attribute above is equal to 0): values ofcomponentRole attribute are as follows: 0=Complete main, 1=Music andEffects, 2=Dialog, 3=Commentary, 4=Visually Impaired, 5=HearingImpaired, 6=Voice-Over, 7-254=reserved, 255=unknown.

For video (when componentType attribute above is equal to 1) values ofcomponentRole attribute are as follows: 0=Primary video, 1=Alternativecamera view, 2=Other alternative video component, 3=Sign language inset,4=Follow subject video, 5=3D video left view, 6=3D video right view,7=3D video depth information, 8=Part of video array <x,y> of <n,m>,9=Follow-Subject metadata, 10-254=reserved, 255=unknown.

For Closed Caption component (when componentType attribute above isequal to 2) values of componentRole attribute are as follows: 0=Normal,1=Easy reader, 2-254=reserved, 255=unknown.

When componentType attribute above is between 3 to 7, inclusive, thecomponentRole can be equal to 255. A meaning of a value of this fieldmay be differently set depending on embodiments.

@atsc:componentProtectedFlag is an attribute that indicates if thiscomponent is protected (e.g. encrypted). When this flag is set to avalue of 1 this component is protected (e.g. encrypted). When this flagis set to a value of 0 this component is not protected (e.g. encrypted).When not present the value of componentProtectedFlag attribute isinferred to be equal to 0. A meaning of a value of this field may bedifferently set depending on embodiments.

@atsc:componentId is an attribute that indicates the identifier of thiscomponent. The value of this attribute can be the same as the asset_idin the MP table corresponding to this component.

@atsc:componentName is an attribute that indicates the human readablename of this component.

The proposed default values may vary depending on embodiments. The “use”column illustrated in the figure relates to each field. Here, M maydenote an essential field, O may denote an optional field, OD may denotean optional field having a default value, and CM may denote aconditional essential field. 0 . . . 1 to 0 . . . N may indicate thenumber of available fields.

Hereinafter, a description will be given of MPD for MMT.

The Media Presentation Description is an SLS metadata fragmentcorresponding to a linear service of a given duration defined by thebroadcaster (for example a single TV program, or the set of contiguouslinear TV programs over a period of time). The contents of the MPDprovide the resource identifiers for segments and the context for theidentified resources within the media presentation. The data structureand semantics of the MPD can be according to the MPD defined by MPEGDASH.

In the present embodiment, an MPD delivered by an MMTP session describesRepresentations delivered over broadband, e.g. in the case of a hybridservice, or to support service continuity in handoff from broadcast tobroadband due to broadcast signal degradation (e.g. driving under amountain or through a tunnel).

Hereinafter, a description will be given of an MMT signaling message forMMT.

When MMTP sessions are used to carry a streaming service, MMT signalingmessages defined by MMT are delivered by MMTP packets according tosignaling message mode defined by MMT. The value of the packet_id fieldof MMTP packets carrying service layer signaling is set to ‘00’ exceptfor MMTP packets carrying MMT signaling messages specific to an asset,which can be set to the same packet_id value as the MMTP packetscarrying the asset. Identifiers referencing the appropriate package foreach service are signaled by the USBD fragment as described above. MMTPackage Table (MPT) messages with matching MMT_package_id can bedelivered on the MMTP session signaled in the SLT. Each MMTP sessioncarries MMT signaling messages specific to its session or each assetdelivered by the MMTP session.

In other words, it is possible to access USBD of the MMTP session byspecifying an IP destination address/port number, etc. of a packethaving the SLS for a particular service in the SLT. As described in theforegoing, a packet ID of an MMTP packet carrying the SLS may bedesignated as a particular value such as 00, etc. It is possible toaccess an MPT message having a matched packet ID using theabove-described package IP information of USBD. As described below, theMPT message may be used to access each service component/asset.

The following MMTP messages can be delivered by the MMTP sessionsignaled in the SLT.

MMT Package Table (MPT) message: This message carries an MP (MMTPackage) table which contains the list of all Assets and their locationinformation as defined by MMT. If an Asset is delivered by a PLPdifferent from the current PLP delivering the MP table, the identifierof the PLP carrying the asset can be provided in the MP table usingphysical layer pipe identifier descriptor. The physical layer pipeidentifier descriptor will be described below.

MMT ATSC3 (MA3) message mmt_atsc3_message( ): This message carriessystem metadata specific for services including service layer signalingas described above. mmt_atsc3_message( ) will be described below.

The following MMTP messages can be delivered by the MMTP sessionsignaled in the SLT, if required.

Media Presentation Information (MPI) message: This message carries anMPI table which contains the whole document or a subset of a document ofpresentation information. An MP table associated with the MPI table alsocan be delivered by this message.

Clock Relation Information (CRI) message: This message carries a CRItable which contains clock related information for the mapping betweenthe NTP timestamp and the MPEG-2 STC. According to a given embodiment,the CRI message may not be delivered through the MMTP session.

The following MMTP messages can be delivered by each MMTP sessioncarrying streaming content.

Hypothetical Receiver Buffer Model message: This message carriesinformation required by the receiver to manage its buffer.

Hypothetical Receiver Buffer Model Removal message: This message carriesinformation required by the receiver to manage its MMT de-capsulationbuffer.

Hereinafter, a description will be given of mmt_atsc3_message( )corresponding to one of MMT signaling messages. An MMT Signaling messagemmt_atsc3_message( ) is defined to deliver information specific toservices according to the present invention described above. Thesignaling message may include message ID, version, and/or length fieldscorresponding to basic fields of the MMT signaling message. A payload ofthe signaling message may include service ID information, content typeinformation, content version information, content compressioninformation and/or URI information. The content type information mayindicate a type of data included in the payload of the signalingmessage. The content version information may indicate a version of dataincluded in the payload, and the content compression information mayindicate a type of compression applied to the data. The URI informationmay have URI information related to content delivered by the message.

Hereinafter, a description will be given of the physical layer pipeidentifier descriptor.

The physical layer pipe identifier descriptor is a descriptor that canbe used as one of descriptors of the MP table described above. Thephysical layer pipe identifier descriptor provides information about thePLP carrying an asset. If an asset is delivered by a PLP different fromthe current PLP delivering the MP table, the physical layer pipeidentifier descriptor can be used as an asset descriptor in theassociated MP table to identify the PLP carrying the asset. The physicallayer pipe identifier descriptor may further include BSID information inaddition to PLP ID information. The BSID may be an ID of a broadcaststream that delivers an MMTP packet for an asset described by thedescriptor.

FIG. 8 illustrates a link layer protocol architecture according to anembodiment of the present invention.

Hereinafter, a link layer will be described.

The link layer is the layer between the physical layer and the networklayer, and transports the data from the network layer to the physicallayer at the sending side and transports the data from the physicallayer to the network layer at the receiving side. The purpose of thelink layer includes abstracting all input packet types into a singleformat for processing by the physical layer, ensuring flexibility andfuture extensibility for as yet undefined input types. In addition,processing within the link layer ensures that the input data can betransmitted in an efficient manner, for example by providing options tocompress redundant information in the headers of input packets. Theoperations of encapsulation, compression and so on are referred to asthe link layer protocol and packets created using this protocol arecalled link layer packets. The link layer may perform functions such aspacket encapsulation, overhead reduction and/or signaling transmission,etc.

Hereinafter, packet encapsulation will be described. Link layer protocolallows encapsulation of any type of packet, including ones such as IPpackets and MPEG-2 TS. Using link layer protocol, the physical layerneed only process one single packet format, independent of the networklayer protocol type (here we consider MPEG-2 TS packet as a kind ofnetwork layer packet.) Each network layer packet or input packet istransformed into the payload of a generic link layer packet.Additionally, concatenation and segmentation can be performed in orderto use the physical layer resources efficiently when the input packetsizes are particularly small or large.

As described in the foregoing, segmentation may be used in packetencapsulation. When the network layer packet is too large to processeasily in the physical layer, the network layer packet is divided intotwo or more segments. The link layer packet header includes protocolfields to perform segmentation on the sending side and reassembly on thereceiving side. When the network layer packet is segmented, each segmentcan be encapsulated to link layer packet in the same order as originalposition in the network layer packet. Also each link layer packet whichincludes a segment of network layer packet can be transported to PHYlayer consequently.

As described in the foregoing, concatenation may be used in packetencapsulation. When the network layer packet is small enough for thepayload of a link layer packet to include several network layer packets,the link layer packet header includes protocol fields to performconcatenation. The concatenation is combining of multiple small sizednetwork layer packets into one payload. When the network layer packetsare concatenated, each network layer packet can be concatenated topayload of link layer packet in the same order as original input order.Also each packet which constructs a payload of link layer packet can bewhole packet, not a segment of packet.

Hereinafter, overhead reduction will be described. Use of the link layerprotocol can result in significant reduction in overhead for transportof data on the physical layer. The link layer protocol according to thepresent invention may provide IP overhead reduction and/or MPEG-2 TSoverhead reduction. In IP overhead reduction, IP packets have a fixedheader format, however some of the information which is needed in acommunication environment may be redundant in a broadcast environment.Link layer protocol provides mechanisms to reduce the broadcast overheadby compressing headers of IP packets. In MPEG-2 TS overhead reduction,link layer protocol provides sync byte removal, null packet deletionand/or common header removal (compression). First, sync byte removalprovides an overhead reduction of one byte per TS packet, secondly anull packet deletion mechanism removes the 188 byte null TS packets in amanner that they can be re-inserted at the receiver and finally a commonheader removal mechanism.

For signaling transmission, in the link layer protocol, a particularformat for the signaling packet may be provided for link layersignaling, which will be described below.

In the illustrated link layer protocol architecture according to anembodiment of the present invention, link layer protocol takes as inputnetwork layer packets such as IPv4, MPEG-2 TS and so on as inputpackets. Future extension indicates other packet types and protocolwhich is also possible to be input in link layer. Link layer protocolalso specifies the format and signaling for any link layer signaling,including information about mapping to specific channel to the physicallayer. Figure also shows how ALP incorporates mechanisms to improve theefficiency of transmission, via various header compression and deletionalgorithms. In addition, the link layer protocol may basicallyencapsulate input packets.

FIG. 9 illustrates a structure of a base header of a link layer packetaccording to an embodiment of the present invention. Hereinafter, thestructure of the header will be described.

A link layer packet can include a header followed by the data payload.The header of a link layer packet can include a base header, and mayinclude an additional header depending on the control fields of the baseheader. The presence of an optional header is indicated from flag fieldsof the additional header. According to a given embodiment, a fieldindicating the presence of an additional header and an optional headermay be positioned in the base header.

Hereinafter, the structure of the base header will be described. Thebase header for link layer packet encapsulation has a hierarchicalstructure. The base header can be two bytes in length and is the minimumlength of the link layer packet header.

The illustrated base header according to the present embodiment mayinclude a Packet_Type field, a PC field and/or a length field. Accordingto a given embodiment, the base header may further include an HM fieldor an S/C field.

Packet_Type field can be a 3-bit field that indicates the originalprotocol or packet type of the input data before encapsulation into alink layer packet. An IPv4 packet, a compressed IP packet, a link layersignaling packet, and other types of packets may have the base headerstructure and may be encapsulated. However, according to a givenembodiment, the MPEG-2 TS packet may have a different particularstructure, and may be encapsulated. When the value of Packet_Type is“000”, “001” “100” or “111”, that is the original data type of an ALPpacket is one of an IPv4 packet, a compressed IP packet, link layersignaling or extension packet. When the MPEG-2 TS packet isencapsulated, the value of Packet_Type can be “010”. Other values of thePacket_Type field may be reserved for future use.

Payload_Configuration (PC) field can be a 1-bit field that indicates theconfiguration of the payload. A value of 0 can indicate that the linklayer packet carries a single, whole input packet and the followingfield is the Header_Mode field. A value of 1 can indicate that the linklayer packet carries more than one input packet (concatenation) or apart of a large input packet (segmentation) and the following field isthe Segmentation_Concatenation field.

Header_Mode (HM) field can be a 1-bit field, when set to 0, that canindicate there is no additional header, and that the length of thepayload of the link layer packet is less than 2048 bytes. This value maybe varied depending on embodiments. A value of 1 can indicate that anadditional header for single packet defined below is present followingthe Length field. In this case, the length of the payload is larger than2047 bytes and/or optional features can be used (sub streamidentification, header extension, etc.). This value may be varieddepending on embodiments. This field can be present only whenPayload_Configuration field of the link layer packet has a value of 0.

Segmentation_Concatenation (S/C) field can be a 1-bit field, when set to0, that can indicate that the payload carries a segment of an inputpacket and an additional header for segmentation defined below ispresent following the Length field. A value of 1 can indicate that thepayload carries more than one complete input packet and an additionalheader for concatenation defined below is present following the Lengthfield. This field can be present only when the value ofPayload_Configuration field of the ALP packet is 1.

Length field can be a 11-bit field that indicates the 11 leastsignificant bits (LSBs) of the length in bytes of payload carried by thelink layer packet. When there is a Length_MSB field in the followingadditional header, the length field is concatenated with the Length_MSBfield, and is the LSB to provide the actual total length of the payload.The number of bits of the length field may be changed to another valuerather than 11 bits.

Following types of packet configuration are thus possible: a singlepacket without any additional header, a single packet with an additionalheader, a segmented packet and a concatenated packet. According to agiven embodiment, more packet configurations may be made through acombination of each additional header, an optional header, an additionalheader for signaling information to be described below, and anadditional header for time extension.

FIG. 10 illustrates a structure of an additional header of a link layerpacket according to an embodiment of the present invention.

Various types of additional headers may be present. Hereinafter, adescription will be given of an additional header for a single packet.

This additional header for single packet can be present when Header_Mode(HM)=“1”. The Header_Mode (HM) can be set to 1 when the length of thepayload of the link layer packet is larger than 2047 bytes or when theoptional fields are used. The additional header for single packet isshown in Figure (tsib10010).

Length_MSB field can be a 5-bit field that can indicate the mostsignificant bits (MSBs) of the total payload length in bytes in thecurrent link layer packet, and is concatenated with the Length fieldcontaining the 11 least significant bits (LSBs) to obtain the totalpayload length. The maximum length of the payload that can be signaledis therefore 65535 bytes. The number of bits of the length field may bechanged to another value rather than 11 bits. In addition, the number ofbits of the Length_MSB field may be changed, and thus a maximumexpressible payload length may be changed. According to a givenembodiment, each length field may indicate a length of a whole linklayer packet rather than a payload.

SIF (Sub stream Identifier Flag) field can be a 1-bit field that canindicate whether the sub stream ID (SID) is present after the HEF fieldor not. When there is no SID in this link layer packet, SIF field can beset to 0. When there is a SID after HEF field in the link layer packet,SIF can be set to 1. The detail of SID is described below.

HEF (Header Extension Flag) field can be a 1-bit field that canindicate, when set to 1 additional header is present for futureextension. A value of 0 can indicate that this extension header is notpresent.

Hereinafter, a description will be given of an additional header whensegmentation is used.

This additional header (tsib10020) can be present whenSegmentation_Concatenation (S/C)=“0”. Segment_Sequence_Number can be a5-bit unsigned integer that can indicate the order of the correspondingsegment carried by the link layer packet. For the link layer packetwhich carries the first segment of an input packet, the value of thisfield can be set to 0x0. This field can be incremented by one with eachadditional segment belonging to the segmented input packet.

Last_Segment_Indicator (LSI) can be a 1-bit field that can indicate,when set to 1, that the segment in this payload is the last one of inputpacket. A value of 0, can indicate that it is not last segment.

SIF (Sub stream Identifier Flag) can be a 1-bit field that can indicatewhether the SID is present after the HEF field or not. When there is noSID in the link layer packet, SIF field can be set to 0. When there is aSID after the HEF field in the link layer packet, SIF can be set to 1.

HEF (Header Extension Flag) can be a This 1-bit field that can indicate,when set to 1, that the optional header extension is present after theadditional header for future extensions of the link layer header. Avalue of 0 can indicate that optional header extension is not present.

According to a given embodiment, a packet ID field may be additionallyprovided to indicate that each segment is generated from the same inputpacket. This field may be unnecessary and thus be omitted when segmentsare transmitted in order.

Hereinafter, a description will be given of an additional header whenconcatenation is used.

This additional header (tsib10030) can be present whenSegmentation_Concatenation (S/C)=“1”.

Length_MSB can be a 4-bit field that can indicate MSB bits of thepayload length in bytes in this link layer packet. The maximum length ofthe payload is 32767 bytes for concatenation. As described in theforegoing, a specific numeric value may be changed.

Count can be a field that can indicate the number of the packetsincluded in the link layer packet. The number of the packets included inthe link layer packet, 2 can be set to this field. So, its maximum valueof concatenated packets in a link layer packet is 9. A scheme in whichthe count field indicates the number may be varied depending onembodiments. That is, the numbers from 1 to 8 may be indicated.

HEF (Header Extension Flag) can be a 1-bit field that can indicate, whenset to 1 the optional header extension is present after the additionalheader for future extensions of the link layer header. A value of 0, canindicate extension header is not present.

Component_Length can be a 12-bit length field that can indicate thelength in byte of each packet. Component_Length fields are included inthe same order as the packets present in the payload except lastcomponent packet. The number of length field can be indicated by(Count+1). According to a given embodiment, length fields, the number ofwhich is the same as a value of the count field, may be present. When alink layer header consists of an odd number of Component_Length, fourstuffing bits can follow after the last Component_Length field. Thesebits can be set to 0. According to a given embodiment, aComponent_length field indicating a length of a last concatenated inputpacket may not be present. In this case, the length of the lastconcatenated input packet may correspond to a length obtained bysubtracting a sum of values indicated by respective Component_lengthfields from a whole payload length.

Hereinafter, the optional header will be described.

As described in the foregoing, the optional header may be added to arear of the additional header. The optional header field can contain SIDand/or header extension. The SID is used to filter out specific packetstream in the link layer level. One example of SID is the role ofservice identifier in a link layer stream carrying multiple services.The mapping information between a service and the SID valuecorresponding to the service can be provided in the SLT, if applicable.The header extension contains extended field for future use. Receiverscan ignore any header extensions which they do not understand.

SID (Sub stream Identifier) can be a 8-bit field that can indicate thesub stream identifier for the link layer packet. If there is optionalheader extension, SID present between additional header and optionalheader extension.

Header_Extension ( ) can include the fields defined below.

Extension Type can be an 8-bit field that can indicate the type of theHeader_Extension ( ).

Extension_Length can be a 8-bit field that can indicate the length ofthe Header Extension ( ) in bytes counting from the next byte to thelast byte of the Header_Extension ( ).

Extension_Byte can be a byte representing the value of theHeader_Extension ( ).

FIG. 11 illustrates a structure of an additional header of a link layerpacket according to another embodiment of the present invention.

Hereinafter, a description will be given of an additional header forsignaling information.

How link layer signaling is incorporated into link layer packets are asfollows. Signaling packets are identified by when the Packet Type fieldof the base header is equal to 100.

Figure (tsib11010) shows the structure of the link layer packetscontaining additional header for signaling information. In addition tothe link layer header, the link layer packet can consist of twoadditional parts, additional header for signaling information and theactual signaling data itself. The total length of the link layersignaling packet is shown in the link layer packet header.

The additional header for signaling information can include followingfields. According to a given embodiment, some fields may be omitted.

Signaling_Type can be an 8-bit field that can indicate the type ofsignaling.

Signaling_Type_Extension can be a 16-bit filed that can indicate theattribute of the signaling. Detail of this field can be defined insignaling specification.

Signaling_Version can be an 8-bit field that can indicate the version ofsignaling.

Signaling_Format can be a 2-bit field that can indicate the data formatof the signaling data. Here, a signaling format may refer to a dataformat such as a binary format, an XML format, etc.

Signaling_Encoding can be a 2-bit field that can specify theencoding/compression format. This field may indicate whether compressionis not performed and which type of compression is performed.

Hereinafter, a description will be given of an additional header forpacket type extension.

In order to provide a mechanism to allow an almost unlimited number ofadditional protocol and packet types to be carried by link layer in thefuture, the additional header is defined. Packet type extension can beused when Packet_type is 111 in the base header as described above.Figure (tsib11020) shows the structure of the link layer packetscontaining additional header for type extension.

The additional header for type extension can include following fields.According to a given embodiment, some fields may be omitted.

extended_type can be a 16-bit field that can indicate the protocol orpacket type of the input encapsulated in the link layer packet aspayload. This field cannot be used for any protocol or packet typealready defined by Packet_Type field.

FIG. 12 illustrates a header structure of a link layer packet for anMPEG-2 TS packet and an encapsulation process thereof according to anembodiment of the present invention.

Hereinafter, a description will be given of a format of the link layerpacket when the MPEG-2 TS packet is input as an input packet.

In this case, the Packet_Type field of the base header is equal to 010.Multiple TS packets can be encapsulated within each link layer packet.The number of TS packets is signaled via the NUMTS field. In this case,as described in the foregoing, a particular link layer packet headerformat may be used.

Link layer provides overhead reduction mechanisms for MPEG-2 TS toenhance the transmission efficiency. The sync byte (0x47) of each TSpacket can be deleted. The option to delete NULL packets and similar TSheaders is also provided.

In order to avoid unnecessary transmission overhead, TS null packets(PID=0x1FFF) may be removed. Deleted null packets can be recovered inreceiver side using DNP field. The DNP field indicates the count ofdeleted null packets. Null packet deletion mechanism using DNP field isdescribed below.

In order to achieve more transmission efficiency, similar header ofMPEG-2 TS packets can be removed. When two or more successive TS packetshave sequentially increased continuity counter fields and other headerfields are the same, the header is sent once at the first packet and theother headers are deleted. HDM field can indicate whether the headerdeletion is performed or not. Detailed procedure of common TS headerdeletion is described below.

When all three overhead reduction mechanisms are performed, overheadreduction can be performed in sequence of sync removal, null packetdeletion, and common header deletion. According to a given embodiment, aperformance order of respective mechanisms may be changed. In addition,some mechanisms may be omitted according to a given embodiment.

The overall structure of the link layer packet header when using MPEG-2TS packet encapsulation is depicted in Figure (tsib12010).

Hereinafter, a description will be given of each illustrated field.Packet_Type can be a 3-bit field that can indicate the protocol type ofinput packet as describe above. For MPEG-2 TS packet encapsulation, thisfield can always be set to 010.

NUMTS (Number of TS packets) can be a 4-bit field that can indicate thenumber of TS packets in the payload of this link layer packet. A maximumof 16 TS packets can be supported in one link layer packet. The value ofNUMTS=0 can indicate that 16 TS packets are carried by the payload ofthe link layer packet. For all other values of NUMTS, the same number ofTS packets are recognized, e.g. NUMTS=0001 means one TS packet iscarried.

AHF (Additional Header Flag) can be a field that can indicate whetherthe additional header is present of not. A value of 0 indicates thatthere is no additional header. A value of 1 indicates that an additionalheader of length 1-byte is present following the base header. If null TSpackets are deleted or TS header compression is applied this field canbe set to 1. The additional header for TS packet encapsulation consistsof the following two fields and is present only when the value of AHF inthis link layer packet is set to 1.

HDM (Header Deletion Mode) can be a 1-bit field that indicates whetherTS header deletion can be applied to this link layer packet. A value of1 indicates that TS header deletion can be applied. A value of “0”indicates that the TS header deletion method is not applied to this linklayer packet.

DNP (Deleted Null Packets) can be a 7-bit field that indicates thenumber of deleted null TS packets prior to this link layer packet. Amaximum of 128 null TS packets can be deleted. When HDM=0 the value ofDNP=0 can indicate that 128 null packets are deleted. When HDM=1 thevalue of DNP=0 can indicate that no null packets are deleted. For allother values of DNP, the same number of null packets are recognized,e.g. DNP=5 means 5 null packets are deleted.

The number of bits of each field described above may be changed.According to the changed number of bits, a minimum/maximum value of avalue indicated by the field may be changed. These numbers may bechanged by a designer.

Hereinafter, SYNC byte removal will be described.

When encapsulating TS packets into the payload of a link layer packet,the SYNC byte (0x47) from the start of each TS packet can be deleted.Hence the length of the MPEG2-TS packet encapsulated in the payload ofthe link layer packet is always of length 187 bytes (instead of 188bytes originally).

Hereinafter, null packet deletion will be described.

Transport Stream rules require that bit rates at the output of atransmitter's multiplexer and at the input of the receiver'sde-multiplexer are constant in time and the end-to-end delay is alsoconstant. For some Transport Stream input signals, null packets may bepresent in order to accommodate variable bitrate services in a constantbitrate stream. In this case, in order to avoid unnecessary transmissionoverhead, TS null packets (that is TS packets with PID=0x1FFF) may beremoved. The process is carried-out in a way that the removed nullpackets can be re-inserted in the receiver in the exact place where theywere originally, thus guaranteeing constant bitrate and avoiding theneed for PCR time stamp updating.

Before generation of a link layer packet, a counter called DNP (DeletedNull-Packets) can first be reset to zero and then incremented for eachdeleted null packet preceding the first non-null TS packet to beencapsulated into the payload of the current link layer packet. Then agroup of consecutive useful TS packets is encapsulated into the payloadof the current link layer packet and the value of each field in itsheader can be determined. After the generated link layer packet isinjected to the physical layer, the DNP is reset to zero. When DNPreaches its maximum allowed value, if the next packet is also a nullpacket, this null packet is kept as a useful packet and encapsulatedinto the payload of the next link layer packet. Each link layer packetcan contain at least one useful TS packet in its payload.

Hereinafter, TS packet header deletion will be described. TS packetheader deletion may be referred to as TS packet header compression.

When two or more successive TS packets have sequentially increasedcontinuity counter fields and other header fields are the same, theheader is sent once at the first packet and the other headers aredeleted. When the duplicated MPEG-2 TS packets are included in two ormore successive TS packets, header deletion cannot be applied intransmitter side. HDM field can indicate whether the header deletion isperformed or not. When TS header deletion is performed, HDM can be setto 1. In the receiver side, using the first packet header, the deletedpacket headers are recovered, and the continuity counter is restored byincreasing it in order from that of the first header.

An example tsib12020 illustrated in the figure is an example of aprocess in which an input stream of a TS packet is encapsulated into alink layer packet. First, a TS stream including TS packets having SYNCbyte (0x47) may be input. First, sync bytes may be deleted through async byte deletion process. In this example, it is presumed that nullpacket deletion is not performed.

Here, it is presumed that packet headers of eight TS packets have thesame field values except for CC, that is, a continuity counter fieldvalue. In this case, TS packet deletion/compression may be performed.Seven remaining TS packet headers are deleted except for a first TSpacket header corresponding to CC=1. The processed TS packets may beencapsulated into a payload of the link layer packet.

In a completed link layer packet, a Packet_Type field corresponds to acase in which TS packets are input, and thus may have a value of 010. ANUMTS field may indicate the number of encapsulated TS packets. An AHFfield may be set to 1 to indicate the presence of an additional headersince packet header deletion is performed. An HDM field may be set to 1since header deletion is performed. DNP may be set to 0 since nullpacket deletion is not performed.

FIG. 13 illustrates an example of adaptation modes in IP headercompression according to an embodiment of the present invention(transmitting side).

Hereinafter, IP header compression will be described.

In the link layer, IP header compression/decompression scheme can beprovided. IP header compression can include two parts: headercompressor/decompressor and adaptation module. The header compressionscheme can be based on the Robust Header Compression (RoHC). Inaddition, for broadcasting usage, adaptation function is added.

In the transmitter side, ROHC compressor reduces the size of header foreach packet. Then, adaptation module extracts context information andbuilds signaling information from each packet stream. In the receiverside, adaptation module parses the signaling information associated withthe received packet stream and attaches context information to thereceived packet stream. ROHC decompressor reconstructs the original IPpacket by recovering the packet header.

The header compression scheme can be based on the RoHC as describedabove. In particular, in the present system, an RoHC framework canoperate in a unidirectional mode (U mode) of the RoHC. In addition, inthe present system, it is possible to use an RoHC UDP header compressionprofile which is identified by a profile identifier of 0x0002.

Hereinafter, adaptation will be described.

In case of transmission through the unidirectional link, if a receiverhas no information of context, decompressor cannot recover the receivedpacket header until receiving full context. This may cause channelchange delay and turn on delay. For this reason, context information andconfiguration parameters between compressor and decompressor can bealways sent with packet flow.

The Adaptation function provides out-of-band transmission of theconfiguration parameters and context information. Out-of-bandtransmission can be done through the link layer signaling. Therefore,the adaptation function is used to reduce the channel change delay anddecompression error due to loss of context information.

Hereinafter, extraction of context information will be described.

Context information may be extracted using various schemes according toadaptation mode. In the present invention, three examples will bedescribed below. The scope of the present invention is not restricted tothe examples of the adaptation mode to be described below. Here, theadaptation mode may be referred to as a context extraction mode.

Adaptation Mode 1 (not illustrated) may be a mode in which no additionaloperation is applied to a basic RoHC packet stream. In other words, theadaptation module may operate as a buffer in this mode. Therefore, inthis mode, context information may not be included in link layersignaling.

In Adaptation Mode 2 (tsib13010), the adaptation module can detect theIR packet from ROHC packet flow and extract the context information(static chain). After extracting the context information, each IR packetcan be converted to an IR-DYN packet. The converted IR-DYN packet can beincluded and transmitted inside the ROHC packet flow in the same orderas IR packet, replacing the original packet.

In Adaptation Mode 3 (tsib13020), the adaptation module can detect theIR and IR-DYN packet from ROHC packet flow and extract the contextinformation. The static chain and dynamic chain can be extracted from IRpacket and dynamic chain can be extracted from IR-DYN packet. Afterextracting the context information, each IR and IR-DYN packet can beconverted to a compressed packet. The compressed packet format can bethe same with the next packet of IR or IR-DYN packet. The convertedcompressed packet can be included and transmitted inside the ROHC packetflow in the same order as IR or IR-DYN packet, replacing the originalpacket.

Signaling (context) information can be encapsulated based ontransmission structure. For example, context information can beencapsulated to the link layer signaling. In this case, the packet typevalue can be set to “100”.

In the above-described Adaptation Modes 2 and 3, a link layer packet forcontext information may have a packet type field value of 100. Inaddition, a link layer packet for compressed IP packets may have apacket type field value of 001. The values indicate that each of thesignaling information and the compressed IP packets are included in thelink layer packet as described above.

Hereinafter, a description will be given of a method of transmitting theextracted context information.

The extracted context information can be transmitted separately fromROHC packet flow, with signaling data through specific physical datapath. The transmission of context depends on the configuration of thephysical layer path. The context information can be sent with other linklayer signaling through the signaling data pipe.

In other words, the link layer packet having the context information maybe transmitted through a signaling PLP together with link layer packetshaving other link layer signaling information (Packet_Type=100).Compressed IP packets from which context information is extracted may betransmitted through a general PLP (Packet_Type=001). Here, depending onembodiments, the signaling PLP may refer to an L1 signaling path. Inaddition, depending on embodiments, the signaling PLP may not beseparated from the general PLP, and may refer to a particular andgeneral PLP through which the signaling information is transmitted.

At a receiving side, prior to reception of a packet stream, a receivermay need to acquire signaling information. When receiver decodes initialPLP to acquire the signaling information, the context signaling can bealso received. After the signaling acquisition is done, the PLP toreceive packet stream can be selected. In other words, the receiver mayacquire the signaling information including the context information byselecting the initial PLP. Here, the initial PLP may be theabove-described signaling PLP. Thereafter, the receiver may select a PLPfor acquiring a packet stream. In this way, the context information maybe acquired prior to reception of the packet stream.

After the PLP for acquiring the packet stream is selected, theadaptation module can detect IR-DYN packet form received packet flow.Then, the adaptation module parses the static chain from the contextinformation in the signaling data. This is similar to receiving the IRpacket. For the same context identifier, IR-DYN packet can be recoveredto IR packet. Recovered ROHC packet flow can be sent to ROHCdecompressor. Thereafter, decompression may be started.

FIG. 14 illustrates a link mapping table (LMT) and an RoHC-U descriptiontable according to an embodiment of the present invention.

Hereinafter, link layer signaling will be described.

Generally, link layer signaling is operates under IP level. At thereceiver side, link layer signaling can be obtained earlier than IPlevel signaling such as Service List Table (SLT) and Service LayerSignaling (SLS). Therefore, link layer signaling can be obtained beforesession establishment.

For link layer signaling, there can be two kinds of signaling accordinginput path: internal link layer signaling and external link layersignaling. The internal link layer signaling is generated in link layerat transmitter side. And the link layer takes the signaling fromexternal module or protocol. This kind of signaling information isconsidered as external link layer signaling. If some signaling need tobe obtained prior to IP level signaling, external signaling istransmitted in format of link layer packet.

The link layer signaling can be encapsulated into link layer packet asdescribed above. The link layer packets can carry any format of linklayer signaling, including binary and XML. The same signalinginformation may not be transmitted in different formats for the linklayer signaling.

Internal link layer signaling may include signaling information for linkmapping. The Link Mapping Table (LMT) provides a list of upper layersessions carried in a PLP. The LMT also provides addition informationfor processing the link layer packets carrying the upper layer sessionsin the link layer.

An example of the LMT (tsib14010) according to the present invention isillustrated.

signaling_type can be an 8-bit unsigned integer field that indicates thetype of signaling carried by this table. The value of signaling_typefield for Link Mapping Table (LMT) can be set to 0x01.

PLP_ID can be an 8-bit field that indicates the PLP corresponding tothis table.

num_session can be an 8-bit unsigned integer field that provides thenumber of upper layer sessions carried in the PLP identified by theabove PLP_ID field. When the value of signaling_type field is 0x01, thisfield can indicate the number of UDP/IP sessions in the PLP.

src_IP_add can be a 32-bit unsigned integer field that contains thesource IP address of an upper layer session carried in the PLPidentified by the PLP_ID field.

dst_IP_add can be a 32-bit unsigned integer field that contains thedestination IP address of an upper layer session carried in the PLPidentified by the PLP_ID field.

src_UDP_port can be a 16-bit unsigned integer field that represents thesource UDP port number of an upper layer session carried in the PLPidentified by the PLP_ID field.

dst_UDP_port can be a 16-bit unsigned integer field that represents thedestination UDP port number of an upper layer session carried in the PLPidentified by the PLP_ID field.

SID_flag can be a 1-bit Boolean field that indicates whether the linklayer packet carrying the upper layer session identified by above 4fields, Src_IP_add, Dst_IP_add, Src_UDP_Port and Dst_UDP_Port, has anSID field in its optional header. When the value of this field is set to0, the link layer packet carrying the upper layer session may not havean SID field in its optional header. When the value of this field is setto 1, the link layer packet carrying the upper layer session can have anSID field in its optional header and the value the SID field can be sameas the following SID field in this table.

compressed_flag can be a 1-bit Boolean field that indicates whether theheader compression is applied the link layer packets carrying the upperlayer session identified by above 4 fields, Src_IP_add, Dst_IP_add,Src_UDP_Port and Dst_UDP_Port. When the value of this field is set to 0,the link layer packet carrying the upper layer session may have a valueof 0x00 of Packet_Type field in its base header. When the value of thisfield is set to 1, the link layer packet carrying the upper layersession may have a value of 0x01 of Packet_Type field in its base headerand the Context_ID field can be present.

SID can be an 8-bit unsigned integer field that indicates sub streamidentifier for the link layer packets carrying the upper layer sessionidentified by above 4 fields, SrcIP_add, Dst_IP_add, Src_UDP_Port andDst_UDP_Port. This field can be present when the value of SID_flag isequal to 1.

context_id can be an 8-bit field that provides a reference for thecontext id (CID) provided in the ROHC-U description table. This fieldcan be present when the value of compressed_flag is equal to 1.

An example of the RoHC-U description table (tsib14020) according to thepresent invention is illustrated. As described in the foregoing, theRoHC-U adaptation module may generate information related to headercompression.

signaling_type can be an 8-bit field that indicates the type ofsignaling carried by this table. The value of signaling_type field forROHC-U description table (RDT) can be set to “0x02”.

PLP_ID can be an 8-bit field that indicates the PLP corresponding tothis table.

context_id can be an 8-bit field that indicates the context id (CID) ofthe compressed IP stream. In this system, 8-bit CID can be used forlarge CID.

context_profile can be an 8-bit field that indicates the range ofprotocols used to compress the stream. This field can be omitted.

adaptation_mode can be a 2-bit field that indicates the mode ofadaptation module in this PLP. Adaptation modes have been describedabove.

context_config can be a 2-bit field that indicates the combination ofthe context information. If there is no context information in thistable, this field may be set to “0x0”. If the static_chain( ) ordynamic_chain( ) byte is included in this table, this field may be setto “0x01” or “0x02” respectively. If both of the static_chain( ) anddynamic_chain( ) byte are included in this table, this field may be setto “0x03”.

context_length can be an 8-bit field that indicates the length of thestatic chain byte sequence. This field can be omitted.

static_chain_byte ( ) can be a field that conveys the static informationused to initialize the ROHC-U decompressor. The size and structure ofthis field depend on the context profile.

dynamic_chain_byte ( ) can be a field that conveys the dynamicinformation used to initialize the ROHC-U decompressor. The size andstructure of this field depend on the context profile.

The static_chain_byte can be defined as sub-header information of IRpacket. The dynamic_chain_byte can be defined as sub-header informationof IR packet and IR-DYN packet.

FIG. 15 illustrates a structure of a link layer on a transmitter sideaccording to an embodiment of the present invention.

The present embodiment presumes that an IP packet is processed. From afunctional point of view, the link layer on the transmitter side maybroadly include a link layer signaling part in which signalinginformation is processed, an overhead reduction part, and/or anencapsulation part. In addition, the link layer on the transmitter sidemay include a scheduler for controlling and scheduling an overalloperation of the link layer and/or input and output parts of the linklayer.

First, signaling information of an upper layer and/or a system parametertsib15010 may be delivered to the link layer. In addition, an IP streamincluding IP packets may be delivered to the link layer from an IP layertsib15110.

As described above, the scheduler tsib15020 may determine and controloperations of several modules included in the link layer. The deliveredsignaling information and/or system parameter tsib15010 may be filtereror used by the scheduler tsib15020. Information, which corresponds to apart of the delivered signaling information and/or system parametertsib15010, necessary for a receiver may be delivered to the link layersignaling part. In addition, information, which corresponds to a part ofthe signaling information, necessary for an operation of the link layermay be delivered to an overhead reduction controller tsib15120 or anencapsulation controller tsib15180.

The link layer signaling part may collect information to be transmittedas a signal in a physical layer, and convert/configure the informationin a form suitable for transmission. The link layer signaling part mayinclude a signaling manager tsib15030, a signaling formatter tsib15040,and/or a buffer for channels tsib15050.

The signaling manager tsib15030 may receive signaling informationdelivered from the scheduler tsib15020 and/or signaling (and/or context)information delivered from the overhead reduction part. The signalingmanager tsib15030 may determine a path for transmission of the signalinginformation for delivered data. The signaling information may bedelivered through the path determined by the signaling managertsib15030. As described in the foregoing, signaling information to betransmitted through a divided channel such as the FIC, the EAS, etc. maybe delivered to the signaling formatter tsib15040, and other signalinginformation may be delivered to an encapsulation buffer tsib15070.

The signaling formatter tsib15040 may format related signalinginformation in a form suitable for each divided channel such thatsignaling information may be transmitted through a separately dividedchannel. As described in the foregoing, the physical layer may includeseparate physically/logically divided channels. The divided channels maybe used to transmit FIC signaling information or EAS-relatedinformation. The FIC or EAS-related information may be sorted by thesignaling manager tsib15030, and input to the signaling formattertsib15040. The signaling formatter tsib15040 may format the informationbased on each separate channel. When the physical layer is designed totransmit particular signaling information through a separately dividedchannel other than the FIC and the EAS, a signaling formatter for theparticular signaling information may be additionally provided. Throughthis scheme, the link layer may be compatible with various physicallayers.

The buffer for channels tsib15050 may deliver the signaling informationreceived from the signaling formatter tsib15040 to separate dedicatedchannels tsib15060. The number and content of the separate channels mayvary depending on embodiments.

As described in the foregoing, the signaling manager tsib15030 maydeliver signaling information, which is not delivered to a particularchannel, to the encapsulation buffer tsib15070. The encapsulation buffertsib15070 may function as a buffer that receives the signalinginformation which is not delivered to the particular channel.

An encapsulation block for signaling information tsib15080 mayencapsulate the signaling information which is not delivered to theparticular channel. A transmission buffer tsib15090 may function as abuffer that delivers the encapsulated signaling information to a DP forsignaling information tsib15100. Here, the DP for signaling informationtsib15100 may refer to the above-described PLS region.

The overhead reduction part may allow efficient transmission by removingoverhead of packets delivered to the link layer. It is possible toconfigure overhead reduction parts corresponding to the number of IPstreams input to the link layer.

An overhead reduction buffer tsib15130 may receive an IP packetdelivered from an upper layer. The received IP packet may be input tothe overhead reduction part through the overhead reduction buffertsib15130.

An overhead reduction controller tsib15120 may determine whether toperform overhead reduction on a packet stream input to the overheadreduction buffer tsib15130. The overhead reduction controller tsib15120may determine whether to perform overhead reduction for each packetstream. When overhead reduction is performed on a packet stream, packetsmay be delivered to a robust header compression (RoHC) compressortsib15140 to perform overhead reduction. When overhead reduction is notperformed on a packet stream, packets may be delivered to theencapsulation part to perform encapsulation without overhead reduction.Whether to perform overhead reduction of packets may be determined basedon the signaling information tsib15010 delivered to the link layer. Thesignaling information may be delivered to the encapsulation controllertsib15180 by the scheduler tsib15020.

The RoHC compressor tsib15140 may perform overhead reduction on a packetstream. The RoHC compressor tsib15140 may perform an operation ofcompressing a header of a packet. Various schemes may be used foroverhead reduction. Overhead reduction may be performed using a schemeproposed by the present invention. The present invention presumes an IPstream, and thus an expression “RoHC compressor” is used. However, thename may be changed depending on embodiments. The operation is notrestricted to compression of the IP stream, and overhead reduction ofall types of packets may be performed by the RoHC compressor tsib15140.

A packet stream configuration block tsib15150 may separate informationto be transmitted to a signaling region and information to betransmitted to a packet stream from IP packets having compressedheaders. The information to be transmitted to the packet stream mayrefer to information to be transmitted to a DP region. The informationto be transmitted to the signaling region may be delivered to asignaling and/or context controller tsib15160. The information to betransmitted to the packet stream may be transmitted to the encapsulationpart.

The signaling and/or context controller tsib15160 may collect signalingand/or context information and deliver the signaling and/or contextinformation to the signaling manager in order to transmit the signalingand/or context information to the signaling region.

The encapsulation part may perform an operation of encapsulating packetsin a form suitable for a delivery to the physical layer. It is possibleto configure encapsulation parts corresponding to the number of IPstreams.

An encapsulation buffer tsib15170 may receive a packet stream forencapsulation. Packets subjected to overhead reduction may be receivedwhen overhead reduction is performed, and an input IP packet may bereceived without change when overhead reduction is not performed.

An encapsulation controller tsib15180 may determine whether toencapsulate an input packet stream. When encapsulation is performed, thepacket stream may be delivered to a segmentation/concatenation blocktsib15190. When encapsulation is not performed, the packet stream may bedelivered to a transmission buffer tsib15230. Whether to encapsulatepackets may be determined based on the signaling information tsib15010delivered to the link layer. The signaling information may be deliveredto the encapsulation controller tsib15180 by the scheduler tsib15020.

In the segmentation/concatenation block tsib15190, the above-describedsegmentation or concatenation operation may be performed on packets. Inother words, when an input IP packet is longer than a link layer packetcorresponding to an output of the link layer, one IP packet may besegmented into several segments to configure a plurality of link layerpacket payloads. On the other hand, when an input IP packet is shorterthan a link layer packet corresponding to an output of the link layer,several IP packets may be concatenated to configure one link layerpacket payload.

A packet configuration table tsib15200 may have configurationinformation of a segmented and/or concatenated link layer packet. Atransmitter and a receiver may have the same information in the packetconfiguration table tsib15200. The transmitter and the receiver mayrefer to the information of the packet configuration table tsib15200. Anindex value of the information of the packet configuration tabletsib15200 may be included in a header of the link layer packet.

A link layer header information block tsib15210 may collect headerinformation generated in an encapsulation process. In addition, the linklayer header information block tsib15210 may collect header informationincluded in the packet configuration table tsib15200. The link layerheader information block tsib15210 may configure header informationaccording to a header structure of the link layer packet.

A header attachment block tsib15220 may add a header to a payload of asegmented and/or concatenated link layer packet. The transmission buffertsib15230 may function as a buffer to deliver the link layer packet to aDP tsib15240 of the physical layer.

The respective blocks, modules, or parts may be configured as onemodule/protocol or a plurality of modules/protocols in the link layer.

FIG. 16 illustrates a structure of a link layer on a receiver sideaccording to an embodiment of the present invention.

The present embodiment presumes that an IP packet is processed. From afunctional point of view, the link layer on the receiver side maybroadly include a link layer signaling part in which signalinginformation is processed, an overhead processing part, and/or adecapsulation part. In addition, the link layer on the receiver side mayinclude a scheduler for controlling and scheduling overall operation ofthe link layer and/or input and output parts of the link layer.

First, information received through a physical layer may be delivered tothe link layer. The link layer may process the information, restore anoriginal state before being processed at a transmitter side, and thendeliver the information to an upper layer. In the present embodiment,the upper layer may be an IP layer.

Information, which is separated in the physical layer and deliveredthrough a particular channel tsib16030, may be delivered to a link layersignaling part. The link layer signaling part may determine signalinginformation received from the physical layer, and deliver the determinedsignaling information to each part of the link layer.

A buffer for channels tsib16040 may function as a buffer that receivessignaling information transmitted through particular channels. Asdescribed in the foregoing, when physically/logically divided separatechannels are present in the physical layer, it is possible to receivesignaling information transmitted through the channels. When theinformation received from the separate channels is segmented, thesegmented information may be stored until complete information isconfigured.

A signaling decoder/parser tsib16050 may verify a format of thesignaling information received through the particular channel, andextract information to be used in the link layer. When the signalinginformation received through the particular channel is encoded, decodingmay be performed. In addition, according to a given embodiment, it ispossible to verify integrity, etc. of the signaling information.

A signaling manager tsib16060 may integrate signaling informationreceived through several paths. Signaling information received through aDP for signaling tsib16070 to be described below may be integrated inthe signaling manager tsib16060. The signaling manager tsib16060 maydeliver signaling information necessary for each part in the link layer.For example, the signaling manager tsib16060 may deliver contextinformation, etc. for recovery of a packet to the overhead processingpart. In addition, the signaling manager tsib16060 may deliver signalinginformation for control to a scheduler tsib16020.

General signaling information, which is not received through a separateparticular channel, may be received through the DP for signalingtsib16070. Here, the DP for signaling may refer to PLS, L1, etc. Here,the DP may be referred to as a PLP. A reception buffer tsib16080 mayfunction as a buffer that receives signaling information delivered fromthe DP for signaling. In a decapsulation block for signaling informationtsib16090, the received signaling information may be decapsulated. Thedecapsulated signaling information may be delivered to the signalingmanager tsib16060 through a decapsulation buffer tsib16100. As describedin the foregoing, the signaling manager tsib16060 may collate signalinginformation, and deliver the collated signaling information to anecessary part in the link layer.

The scheduler tsib16020 may determine and control operations of severalmodules included in the link layer. The scheduler tsib16020 may controleach part of the link layer using receiver information tsib16010 and/orinformation delivered from the signaling manager tsib16060. In addition,the scheduler tsib16020 may determine an operation mode, etc. of eachpart. Here, the receiver information tsib16010 may refer to informationpreviously stored in the receiver. The scheduler tsib16020 may useinformation changed by a user such as channel switching, etc. to performa control operation.

The decapsulation part may filter a packet received from a DP tsib16110of the physical layer, and separate a packet according to a type of thepacket. It is possible to configure decapsulation parts corresponding tothe number of DPs that can be simultaneously decoded in the physicallayer.

The decapsulation buffer tsib16100 may function as a buffer thatreceives a packet stream from the physical layer to performdecapsulation. A decapsulation controller tsib16130 may determinewhether to decapsulate an input packet stream. When decapsulation isperformed, the packet stream may be delivered to a link layer headerparser tsib16140. When decapsulation is not performed, the packet streammay be delivered to an output buffer tsib16220. The signalinginformation received from the scheduler tsib16020 may be used todetermine whether to perform decapsulation.

The link layer header parser tsib16140 may identify a header of thedelivered link layer packet. It is possible to identify a configurationof an IP packet included in a payload of the link layer packet byidentifying the header. For example, the IP packet may be segmented orconcatenated.

A packet configuration table tsib16150 may include payload informationof segmented and/or concatenated link layer packets. The transmitter andthe receiver may have the same information in the packet configurationtable tsib16150. The transmitter and the receiver may refer to theinformation of the packet configuration table tsib16150. It is possibleto find a value necessary for reassembly based on index informationincluded in the link layer packet.

A reassembly block tsib16160 may configure payloads of the segmentedand/or concatenated link layer packets as packets of an original IPstream. Segments may be collected and reconfigured as one IP packet, orconcatenated packets may be separated and reconfigured as a plurality ofIP packet streams. Recombined IP packets may be delivered to theoverhead processing part.

The overhead processing part may perform an operation of restoring apacket subjected to overhead reduction to an original packet as areverse operation of overhead reduction performed in the transmitter.This operation may be referred to as overhead processing. It is possibleto configure overhead processing parts corresponding to the number ofDPs that can be simultaneously decoded in the physical layer.

A packet recovery buffer tsib16170 may function as a buffer thatreceives a decapsulated RoHC packet or IP packet to perform overheadprocessing.

An overhead controller tsib16180 may determine whether to recover and/ordecompress the decapsulated packet. When recovery and/or decompressionare performed, the packet may be delivered to a packet stream recoveryblock tsib16190. When recovery and/or decompression are not performed,the packet may be delivered to the output buffer tsib16220. Whether toperform recovery and/or decompression may be determined based on thesignaling information delivered by the scheduler tsib16020.

The packet stream recovery block tsib16190 may perform an operation ofintegrating a packet stream separated from the transmitter with contextinformation of the packet stream. This operation may be a process ofrestoring a packet stream such that an RoHC decompressor tsib16210 canperform processing. In this process, it is possible to receive signalinginformation and/or context information from a signaling and/or contextcontroller tsib16200. The signaling and/or context controller tsib16200may determine signaling information delivered from the transmitter, anddeliver the signaling information to the packet stream recovery blocktsib16190 such that the signaling information may be mapped to a streamcorresponding to a context ID.

The RoHC decompressor tsib16210 may restore headers of packets of thepacket stream. The packets of the packet stream may be restored to formsof original IP packets through restoration of the headers. In otherwords, the RoHC decompressor tsib16210 may perform overhead processing.

The output buffer tsib16220 may function as a buffer before an outputstream is delivered to an IP layer tsib16230.

The link layers of the transmitter and the receiver proposed in thepresent invention may include the blocks or modules described above. Inthis way, the link layer may independently operate irrespective of anupper layer and a lower layer, overhead reduction may be efficientlyperformed, and a supportable function according to an upper/lower layermay be easily defined/added/deleted.

FIG. 17 illustrates a configuration of signaling transmission through alink layer according to an embodiment of the present invention(transmitting/receiving sides).

In the present invention, a plurality of service providers(broadcasters) may provide services within one frequency band. Inaddition, a service provider may provide a plurality of services, andone service may include one or more components. It can be consideredthat the user receives content using a service as a unit.

The present invention presumes that a transmission protocol based on aplurality of sessions is used to support an IP hybrid broadcast.Signaling information delivered through a signaling path may bedetermined based on a transmission configuration of each protocol.Various names may be applied to respective protocols according to agiven embodiment.

In the illustrated data configuration tsib17010 on the transmittingside, service providers (broadcasters) may provide a plurality ofservices (Service #1, #2,). In general, a signal for a service may betransmitted through a general transmission session (signaling C).However, the signal may be transmitted through a particular session(dedicated session) according to a given embodiment (signaling B).

Service data and service signaling information may be encapsulatedaccording to a transmission protocol. According to a given embodiment,an IP/UDP layer may be used. According to a given embodiment, a signalin the IP/UDP layer (signaling A) may be additionally provided. Thissignaling may be omitted.

Data processed using the IP/UDP may be input to the link layer. Asdescribed in the foregoing, overhead reduction and/or encapsulation maybe performed in the link layer. Here, link layer signaling may beadditionally provided. Link layer signaling may include a systemparameter, etc. Link layer signaling has been described above.

The service data and the signaling information subjected to the aboveprocess may be processed through PLPs in a physical layer. Here, a PLPmay be referred to as a DP. The example illustrated in the figurepresumes a case in which a base DP/PLP is used. However, depending onembodiments, transmission may be performed using only a general DP/PLPwithout the base DP/PLP.

In the example illustrated in the figure, a particular channel(dedicated channel) such as an FIC, an EAC, etc. is used. A signaldelivered through the FIC may be referred to as a fast information table(FIT), and a signal delivered through the EAC may be referred to as anemergency alert table (EAT). The FIT may be identical to theabove-described SLT. The particular channels may not be used dependingon embodiments. When the particular channel (dedicated channel) is notconfigured, the FIT and the EAT may be transmitted using a general linklayer signaling transmission scheme, or transmitted using a PLP via theIP/UDP as other service data.

According to a given embodiment, system parameters may include atransmitter-related parameter, a service provider-related parameter,etc. Link layer signaling may include IP header compression-relatedcontext information and/or identification information of data to whichthe context is applied. Signaling of an upper layer may include an IPaddress, a UDP number, service/component information, emergencyalert-related information, an IP/UDP address for service signaling, asession ID, etc. Detailed examples thereof have been described above.

In the illustrated data configuration tsib17020 on the receiving side,the receiver may decode only a PLP for a corresponding service usingsignaling information without having to decode all PLPs.

First, when the user selects or changes a service desired to bereceived, the receiver may be tuned to a corresponding frequency and mayread receiver information related to a corresponding channel stored in aDB, etc. The information stored in the DB, etc. of the receiver may beconfigured by reading an SLT at the time of initial channel scan.

After receiving the SLT and the information about the correspondingchannel, information previously stored in the DB is updated, andinformation about a transmission path of the service selected by theuser and information about a path, through which component informationis acquired or a signal necessary to acquire the information istransmitted, are acquired. When the information is not determined to bechanged using version information of the SLT, decoding or parsing may beomitted.

The receiver may verify whether SLT information is included in a PLP byparsing physical signaling of the PLP in a corresponding broadcaststream (not illustrated), which may be indicated through a particularfield of physical signaling. It is possible to access a position atwhich a service layer signal of a particular service is transmitted byaccessing the SLT information. The service layer signal may beencapsulated into the IP/UDP and delivered through a transmissionsession. It is possible to acquire information about a componentincluded in the service using this service layer signaling. A specificSLT-SLS configuration is as described above.

In other words, it is possible to acquire transmission path information,for receiving upper layer signaling information (service signalinginformation) necessary to receive the service, corresponding to one ofseveral packet streams and PLPs currently transmitted on a channel usingthe SLT. The transmission path information may include an IP address, aUDP port number, a session ID, a PLP ID, etc. Here, depending onembodiments, a value previously designated by the IANA or a system maybe used as an IP/UDP address. The information may be acquired using ascheme of accessing a DB or a shared memory, etc.

When the link layer signal and service data are transmitted through thesame PLP, or only one PLP is operated, service data delivered throughthe PLP may be temporarily stored in a device such as a buffer, etc.while the link layer signal is decoded.

It is possible to acquire information about a path through which theservice is actually transmitted using service signaling information of aservice to be received. In addition, a received packet stream may besubjected to decapsulation and header recovery using information such asoverhead reduction for a PLP to be received, etc.

In the illustrated example (tsib17020), the FIC and the EAC are used,and a concept of the base DP/PLP is presumed. As described in theforegoing, concepts of the FIC, the EAC, and the base DP/PLP may not beused.

FIG. 18 illustrates an interface of a link layer according to anembodiment of the present invention.

The figure shows a case in which a transmitter uses an IP packet and/oran MPEG2-TS packet used in digital broadcast as an input signal. Thetransmitter may support a packet structure in a new protocol which canbe used in future broadcast systems. Encapsulated data and/or signalinginformation of the link layer may be transmitted to a physical layer.The transmitter may process transmitted data (which can includesignaling data) according to a protocol of the physical layer, which issupported by a broadcast system, and transmit a signal including thedata.

A receiver restores the data and/or the signaling information receivedfrom the physical layer to data that can be processed in an upper layer.The receiver can read packet headers and determine whether packetsreceived from the physical layer include signaling information (orsignaling data) or general data (or content data).

The signaling information (i.e., signaling data) transmitted from thetransmitter may include first signaling information which is receivedfrom an upper layer and needs to be transmitted to an upper layer of thereceiver, second signaling information which is generated in the linklayer and provides information related to data processing in the linklayer of the receiver and/or third signaling information which isgenerated in the upper layer or the link layer and transmitted torapidly identify specific data (e.g. service, content and/or signalingdata) in the physical layer.

According to an embodiment of the present invention, additionalprocessing may be performed on packets, delivered from the upper layer,in the link layer.

When a packet delivered from the upper layer is an IP packet, thetransmitter can perform IP header compression in the link layer.Overhead can be reduced in IP flow through IP header compression. For IPheader compression, robust header compression (RoHC) may be used. Referto RFC3095 and RFC5795 for details of RoHC.

In one embodiment of the present invention, RoHC can operate in aunidirectional mode. This will be described in detail later.

When the packet delivered from the upper layer is an MPEG-2 transportstream (ST) packet, overhead reduction may be performed on the MPEG-2 TSpacket. The MPEG-2 TS packet may include a sync field, a null packetand/or a common packet identifier (PID). Since such data is repeated ineach TS packet or unnecessary data, the transmitter can delete the datain the link layer, generate information used for the receiver to restorethe data and transmit the information to the receiver.

The transmitter can encapsulate the packet, transmitted from the upperlayer, in the link layer. For example, the transmitter can generate alink layer packet by encapsulating the IP packet, the MPEG-2 TS packetand/or a packet in a different protocol in the link layer. Packets inone format can be processed in the physical layer of thetransmitter/receiver through encapsulation in the link layerirrespective of protocol type of the network layer. In this case, theMPEG-2 TS packet can be considered to be a packet of the network layer.

The network layer is an upper layer of the link layer. A packet of thenetwork layer can be converted into a payload of a packet of the linklayer. In an embodiment of the present invention, packets of the networklayer can be included in packets of the link layer by being concatenatedand segmented in order to efficiently use resources of the physicallayer.

When the size of packets of the network layer is small such that apayload of the link layer can include a plurality of packets of thenetwork layer, a packet header of the link layer can include a protocolfield for performing concatenation. Concatenation can be defined ascombination of a plurality of packets of the network layer in a payload(a packet payload of the link layer).

When the size of one packet of the network layer is too large to beprocessed in the physical layer, a packet of the network layer may besegmented into two or more segments. A packet header of the link layermay include necessary information in the form of a protocol field suchthat the transmitting side can segment the packet of the network layerand the receiving side can reassemble the segmented packets.

Processing of the link layer in the transmitter includes transmission ofsignaling information generated in the link layer, such as a fastinformation channel (FIC), an emergency alert system (EAS) messageand/or information for overhead reduction.

The FIC is a signaling structure including information necessary forchannel scan and fast service acquisition. That is, a main purpose ofthe FIC is to efficiently transfer information necessary for fastchannel scan and service acquisition. Information included in the FICmay correspond to information for connecting a data pipe (DP) (or PLP)and a broadcast service.

Processing of the link layer in the transmitter includes transmission ofan emergency alert message and signaling information related theretothrough a specific channel. The specific channel may correspond to achannel predefined in the physical layer. The specific channel may becalled an emergency alert channel (EAC).

FIG. 19 illustrates operation of a normal mode from among operationmodes of a link layer according to an embodiment of the presentinvention.

The link layer proposed by the present invention may have variousoperation modes for compatibility between an upper layer and a lowerlayer. The present invention proposes the normal mode and a transparentmode of the link layer. The two operation modes can coexist in the linklayer and which mode will be used can be designated using a signaling orsystem parameter. According to an embodiment, only one of the two modesmay be implemented. Different modes may be applied according to an IPlayer and a TS layer input to the link layer. Otherwise, different modesmay be applied for streams of the IP layer and streams of the TS layer.

According to an embodiment, a new operation mode may be added to thelink layer. The new operation mode may be added on the basis ofconfigurations of an upper layer and a lower layer. The new operationmode may include different interfaces on the basis of the configurationsof the upper layer and the lower layer. Whether to use the new operationmode may be designated using a signaling or system parameter.

In the normal mode, data is processed according to functions supportedby the link layer and then delivered to the physical layer.

First, packets may be respectively transferred from an IP layer, anMPEG-2 TS layer and a specific protocol layer t89010 to the link layer.That is, an IP packet can be delivered from the IP layer to the linklayer. An MPEG-2 TS packet can be delivered from the MPEG-2 TS layer tothe link layer. A specific packet can be delivered from the specificprotocol layer to the link layer.

The delivered packets may or may not be overhead-reduced t89020 and thenencapsulated t89030.

Specifically, the IP packet may or may not be overhead-reduced t89020and then encapsulated t89030. Whether overhead reduction is performedmay be designated by a signaling or system parameter. According to anembodiment, overhead reduction may or may not be performed per IPstream. The encapsulated IP packet can be delivered to the physicallayer.

The MPEG-2 TS packet may be overhead-reduced t89020 and thenencapsulated t89030. In the case of the MPEG-2 TS packet, overheadreduction may be omitted according to an embodiment. However, since ageneral TS packet has a sync byte (0x47) at the head thereof, it may beefficient to remove such fixed overhead. The encapsulated TS packet canbe delivered to the physical layer.

A packet other than the IP or TS packet may or may not beoverhead-reduced t89020 and then encapsulated t89030. Whether overheadreduction is performed may be determined according to characteristics ofthe packet. Whether overhead reduction is performed may be designated bythe signaling or system parameter. The encapsulated packet can bedelivered to the physical layer.

During overhead reduction t89020, the sizes of the input packets may bereduced through an appropriate method. During the overhead reductionprocess, specific information may be extracted or generated from theinput packets. The specific information is information related tosignaling and may be transmitted through a signaling region. Thesignaling information enables the receiver to restore the packetschanged during overhead reduction to the original packets. The signalinginformation can be delivered through link layer signaling t89050.

Link layer signaling t89050 can transmit and manage the signalinginformation extracted/generated during overhead reduction. The physicallayer may have physically/logically separated transmission paths. Linklayer signaling t89050 may deliver the signaling information to thephysical layer according to the separated transmission paths. Theseparated transmission paths may include FIC signaling t89060 and EASsignaling t89070. Signaling information which is not transmitted throughthe transmission paths may be delivered to the physical layer afterbeing subjected to encapsulation t89030.

Signaling information managed through link layer signaling t89050 mayinclude signaling information delivered from an upper layer, signalinginformation generated in the link layer and/or system parameters.Specifically, signaling information managed through link layer signalingt89050 may include signaling information that is delivered from theupper layer and needs to be transmitted to an upper layer of thereceiver, signaling information that is generated in the link layer andneeds to be used in the link layer of the receiver and signalinginformation that is generated in the upper layer or the link layer andused for fast detection in the physical layer of the receiver.

Data encapsulated t89030 and delivered to the physical layer may betransmitted through a data pipe (DP) 89040. Here, the DP may be aphysical layer pipe (PLP). Signaling information transmitted through theaforementioned separate transmission paths may be delivered torespective transmission paths. For example, FIC signaling informationcan be transmitted through an FIC channel t89080 designated in aphysical frame and EAS signaling information can be transmitted throughan EAS channel t89090 designed in the physical frame. Informationrepresenting presence of a specific channel such as an FIC or EAC can besignaled and transmitted through a preamble region of the physical frameor signaled by scrambling a preamble using a specific scramblingsequence. According to an embodiment, FIC signaling/EAS signalinginformation may be transmitted through a normal DP region, a PLS regionor a preamble instead of a designated specific channel.

The receiver can receive data and signaling information through thephysical layer. The receiver can restore the data and signalinginformation to forms that can be processed in an upper layer andtransfer the same to the upper layer. This process can be performed inthe link layer of the receiver. The receiver can determine whetherreceived packets are related to the signaling information or the data byreading headers of the packets, for example. When overhead reduction hasbeen performed at the transmitting side, the receiver can restorepackets having reduced overhead through overhead reduction to theoriginal packets. In this process, the received signaling informationcan be used.

FIG. 20 illustrates operation of the transparent mode from among theoperation modes of the link layer according to an embodiment of thepresent invention.

In the transparent mode, data can be delivered to the physical layerwithout being processed according to functions supported by the linklayer or processed according to only some of the functions and thendelivered to the physical layer. That is, packets delivered from anupper layer can be sent to the physical layer without passing throughoverhead reduction and/or encapsulation in the transparent mode. Otherpackets may be pass through overhead reduction and/or encapsulation inthe transparent mode as necessary. The transparent mode may be called abypass mode.

According to an embodiment, some packets can be processed in the normalmode and some packets can be processed in the transparent mode on thebasis of characteristics of packets and system operation.

Packets to which the transparent mode is applicable may be packets oftypes well known to the system. When the corresponding packets can beprocessed in the physical layer, the transparent mode can be used. Forexample, in the case of a known TS or IP packet, the packet can passthrough overhead reduction and input formatting processes in thephysical layer and thus the transparent mode can be used in the linklayer stage. When the transparent mode is applied and the packet isprocess through input formatting in the physical layer, theaforementioned operation such as TS header compression can be performedin the physical layer. When a normal mode is applied, a processed linklayer packet can be processed by being handled as a GS packet in thephysical layer.

Even in the transparent mode, a link layer signaling module may beprovided when it is necessary to support transmission of signalinginformation. The link layer signaling module can transmit and managesignaling information, as described above. Singling information can beencapsulated and transmitted through a DP and FIC and EAS signalinginformation having separated transmission paths can be respectivelytransmitted through an FIC channel and an EAC channel.

In the transparent mode, whether information corresponds to signalinginformation can be indicated through a method of using a fixed IPaddress and port number, for example. In this case, the signalinginformation may be filtered to configure a link layer packet and thenthe link layer packet may be transmitted through the physical layer.

FIG. 21 illustrates a process of controlling operation modes of thetransmitter and/or the receiver in the link layer according to anembodiment of the present invention.

Determination of a link layer operation mode of the transmitter or thereceiver can enable more efficient use of a broadcast system andflexible design of the broadcast system. According to the method ofcontrolling link layer modes, proposed by the present invention, linklayer modes for efficient operation of a system bandwidth and processingtime can be dynamically switched. In addition, when a specific modeneeds to be supported or need for a specific mode disappears due tochange of the physical layer, this can be easily handled. Furthermore,when a broadcaster providing broadcast services intends to designate amethod for transmitting the broadcast services, broadcast systems caneasily accept requests of the broadcaster.

The method for controlling link layer operation modes may be implementedsuch that the method is performed only in the link layer or may beperformed through data structure change in the link layer. In this case,independent operations of the network layer and/or the physical layercan be performed without additionally implementing additional functionstherein. It is possible to control link layer modes proposed by thepresent invention with signaling or system internal parameters withoutmodifying the system to adapt to the structure of the physical layer. Aspecific mode may operate only when processing of corresponding input issupported in the physical layer.

The figure shows a flow through which the transmitter/receiver processessignals and/or data in the IP layer, link layer and physical layer.

A functional block (which can be implemented as hardware and/orsoftware) for mode control may be added to the link layer to manageparameters and/or signaling information for determining whether toprocess a packet. The link layer can determine whether to execute acorresponding function in a packet stream processing procedure usinginformation stored in the mode control functional block.

Operation of the transmitted will now be described first.

When an IP stream is input to the link layer, the transmitter determineswhether to perform overhead reduction j16020 using mode controlparameters j16005 (j16010). The mode control parameters can be generatedin the transmitter by a service provider. The mode control parameterswill be described in detail later.

When overhead reduction j16020 is performed, information about overheadreduction is generated and included in link layer signaling informationj16060. The link layer signaling information j16060 may include all orsome mode control parameters. The link layer signaling informationj16060 may be delivered in the form of a link layer signaling packet.While the link layer signaling packet can be mapped to a DP anddelivered to the receiver, the link layer signaling packet may betransmitted to the receiver through a predetermined region of abroadcast signal without being mapped to a DP.

The packet stream that has passed through overhead reduction j16020 isencapsulated j16030 and applied to a DP of the physical layer (J16040).When the packet stream has not passed through overhead reduction, thetransmitter determines whether to perform encapsulation j16050 on thepacket stream.

The packet stream that has passed through encapsulation j16030 isapplied to the DP of the physical layer (j16040). Here, operation forgeneral packet (link layer packet) processing is performed in thephysical layer. When the IP stream has not passed through overheadreduction and encapsulation, the IP stream is directly delivered to thephysical layer. Then, operation for processing the IP stream isperformed in the physical layer. When the IP stream is directlytransmitted to the physical layer, parameters can be provided such thatoperation is performed only when the physical layer supports IP packetinput. That is, mode control parameter values can be controlled suchthat operation of directly transmitting an IP packet to the physicallayer is not performed when the physical layer does not support IPpacket processing.

The transmitter transmits the broadcast signal that has passed throughthe aforementioned process to the receiver.

Operation of the receiver will now be described.

When a specific DP is selected according to channel change by a user anda packet stream is received through the DP in the receiver (j16110), thereceiver can check a mode in which the corresponding packet has beengenerated when transmitted using the header of the packet stream and/orsignaling information (S16120). When the mode is confirmed for the DP,the corresponding IP packet is transmitted to the upper layer throughdecapsulation j16130 and overhead reduction j16140 in the link layer.Overhead reduction j16140 may include overhead recovery.

FIG. 22 illustrates operation in the link layer and format of a packettransmitted to the physical layer on the basis of flag values accordingto an embodiment of the present invention.

To determine an operation mode of the link layer, the aforementionedsignaling method can be used. Signaling information related to themethod can be directly transmitted to the receiver. In this case, theaforementioned signaling data or link layer signaling packet may includemode control related information which will be described later.

There may be a method of indirectly signaling an operation mode of thelink layer to the receiver in consideration of complexity of thereceiver.

The following two flags can be considered for operation mode control.

-   -   Header compression flag (HCF): this is a flag setting whether to        apply header compression in the link layer and can be assigned        values indicating “enable” and “disable”.    -   Encapsulation flag (EF): this is a flag setting whether to apply        encapsulation in the link layer and can be assigned values        indicating “enable” and “disable”. However, the EF can be        subordinated to the HCF when encapsulation needs to be        essentially performed according to header compression scheme.

A value mapped to each flag can be provided in the range includingrepresentation of “enable” and “disable” according to systemconfiguration and the number of bits allocated per flag can be changed.For example, the value “enable” can be mapped to 1 and the value“disable” can be mapped to 0.

The figure shows whether header compression and encapsulation areperformed and a packet format transferred to the physical layeraccording to header compression and encapsulation on the basis of HCFand EF values. That is, according to one embodiment of the presentinvention, the receiver can recognize the format of a packet input tothe physical layer from information about the HCF and the EF.

FIG. 23 illustrates an IP overhead reduction process in thetransmitter/receiver according to an embodiment of the presentinvention.

According to an embodiment of the present invention, when an IP streamenters the overhead reduction process, an RoHC compressor L5010 canperform header compression on the IP stream. RoHC can be used as aheader compression algorithm in an embodiment of the present invention.The packet stream that has passed through RoHC can be reconfiguredaccording to an RoHC packet format in a packet stream configurationprocess L5020, and the reconfigured RoHC packet stream can be deliveredto an encapsulation layer L5040 and then transmitted to the receiverthrough the physical layer. RoHC context information and/or signalinginformation generated during packet stream reconfiguration can be madeinto data in a transmittable form through a signaling generator L5030and the data can be delivered to an encapsulation layer or signalingmodule S5050 according to transmission form.

According to an embodiment of the present invention, the receiver canreceive a stream with respect to service data and a signaling channel orsignaling data transmitted through a separate DP. A signaling parserL5060 can receive the signaling data, parses the signaling data intoRoHC context information and/or signaling information and transmit theparsed information to a packet stream recovery unit L5070. The receivercan recover the packet stream reconfigured in the transmitter in aformat that can be decompressed by an RoHC decompressor L5080 using theRoHC context information and/or the signaling information included inthe signaling data, through the packet stream recovery unit L5070. TheRoHC decompressor L5080 can convert the recovered RoHC packet streaminto an IP stream, and the IP stream can be delivered to an upper layerthrough the IP layer.

FIG. 24 illustrates RoHC profiles according to an embodiment of thepresent invention.

According to an embodiment of the present invention, RoHC can be usedfor header compression for an upper packet in the link layer, asdescribed above. An RoHC framework can operate in the unidirectionalmode, as described in RFC 3095, in consideration of characteristics ofbroadcast networks. The RoHC framework defines a plurality of headercompression profiles. Each profile indicates a specific protocolcombination and a profile identifier identifying each profile can beallocated by the Internet assigned numbers authority. Some of theprofiles shown in FIG. 24 can be used in the broadcast system accordingto embodiments of the present invention.

FIG. 25 illustrates processes of configuring and recovering an RoHCpacket stream with respect to configuration mode #1 according to anembodiment of the present invention.

A description will be given of an RoHC packet stream configurationprocess in a transmitter according to an embodiment of the presentinvention.

The transmitter according to an embodiment can detect IR packets andIR-DYN packets from an RoHC packet stream L10010 on the basis of RoHCheader information. Then the transmitter can generate general headercompressed packets using sequence numbers included in the IR packets andthe IR-DYN packets. The general header compressed packets can berandomly generated since the general header compressed packets includesequence number (SN) information irrespective of the type thereof. Here,the SN corresponds to information that is basically present in the RTP.In the case of the UDP, the transmitter can generate and use the SN. Thetransmitter can replace the IR packets or the IR-DYN packets with thegenerated general header compressed packets, extract a static chain anda dynamic chain from the IR packets and extract a dynamic chain from theIR-DYN packets. The extracted static chain and dynamic chain can betransported through out-of-band L10030. The transmitter can replace IRheaders and IR-DYN headers with headers of general header compressedpackets and extract static chains and/or dynamic chains, for all RoHCpacket streams, according to the aforementioned process. A reconfiguredpacket stream L10020 can be transmitted through a data pipe and theextracted static chain and dynamic chain can be transported throughout-of-band L10030.

A description will be given of a process of recovering an RoHC packetstream in a receiver according to an embodiment of the presentinvention.

The receiver according to an embodiment of the present invention canselect a data pipe corresponding to a packet stream to be received usingsignaling information. Then, the receiver can receive the packet streamtransmitted through the data pipe (S10040) and detect a static chain anda dynamic chain corresponding to the packet stream. Here, the staticchain and/or the dynamic chain can be received through out-of-band(S10050). Subsequently, the receiver can detect general headercompressed packets having the same SN as that of the static chain or thedynamic chain from the packet stream transmitted through the data pipe,using SNs of the detected static chain and the dynamic chain. Thereceiver can configure IR packets and/or IR-DYN packets by combining thedetected general header compressed packets with the static chain and/orthe dynamic chain. The configured IR packets and/or the IR-DYN packetscan be transmitted to an RoHC decompressor. In addition, the receivercan configure an RoHC packet stream L10060 including the IR packets, theIR-DYN packets and/or the general header compressed packets. Theconfigured RoHC packet stream can be transmitted to the RoHCdecompressor. The receiver according to an embodiment of the presentinvention can recover the RoHC packet stream using the static chain, thedynamic chain, SNs and/or context IDs of the IR packets and the IR-DYNpackets.

FIG. 26 illustrates processes of configuring and recovering an RoHCpacket stream with respect to configuration mode #2 according to anembodiment of the present invention.

A description will be given of an RoHC packet stream configurationprocess in a transmitter according to an embodiment of the presentinvention.

The transmitter according to an embodiment can detect IR packets andIR-DYN packets from an RoHC packet stream L11010 on the basis of RoHCheader information. Then the transmitter can generate general headercompressed packets using sequence numbers included in the IR packets andthe IR-DYN packets. The general header compressed packets can berandomly generated since the general header compressed packets includesequence number (SN) information irrespective of the type thereof. Here,the SN corresponds to information that is basically present in the RTP.In the case of the UDP, the transmitter can generate and use the SN. Thetransmitter can replace the IR packets or the IR-DYN packets with thegenerated general header compressed packets, extract a static chain fromthe IR packets and extract a dynamic chain from the IR-DYN packets. Theextracted static chain and dynamic chain can be transported throughout-of-band L11030. The transmitter can replace IR headers and IR-DYNheaders with headers of general header compressed packets and extractstatic chains and/or dynamic chains, for all RoHC packet streams,according to the aforementioned process. A reconfigured packet streamL11020 can be transmitted through a data pipe and the extracted staticchain and dynamic chain can be transported through out-of-band L11030.

A description will be given of a process of recovering an RoHC packetstream in a receiver according to an embodiment of the presentinvention.

The receiver according to an embodiment of the present invention canselect a data pipe corresponding to a packet stream to be received usingsignaling information. Then, the receiver can receive the packet streamtransmitted through the data pipe (S11040) and detect a static chain anda dynamic chain corresponding to the packet stream. Here, the staticchain and/or the dynamic chain can be received through out-of-band(S11050). Subsequently, the receiver can detect general headercompressed packets having the same SN as that of the static chain or thedynamic chain from the packet stream transmitted through the data pipe,using SNs of the detected static chain and the dynamic chain. Thereceiver can configure IR packets and/or IR-DYN packets by combining thedetected general header compressed packets with the static chain and/orthe dynamic chain. The configured IR packets and/or the IR-DYN packetscan be transmitted to an RoHC decompressor. In addition, the receivercan configure an RoHC packet stream L11060 including the IR packets, theIR-DYN packets and/or the general header compressed packets. Theconfigured RoHC packet stream can be transmitted to the RoHCdecompressor. The receiver according to an embodiment of the presentinvention can recover the RoHC packet stream using the static chain, thedynamic chain, SNs and/or context IDs of the IR packets and the IR-DYNpackets.

FIG. 27 illustrates processes of configuring and recovering an RoHCpacket stream with respect to configuration mode #2 according to anembodiment of the present invention.

A description will be given of an RoHC packet stream configurationprocess in a transmitter according to an embodiment of the presentinvention.

The transmitter according to an embodiment can detect IR packets from anRoHC packet stream L12010 on the basis of RoHC header information. Then,the transmitter can extract a static chain from the IR packets andconvert the IR packets into IR-DYN packets using parts of the IR packetsother than the extracted static chain. The transmitter can replaceheaders of IR packets with headers of IR-DYN packets and extract staticchains, for all RoHC packet streams, according to the aforementionedprocess. A reconfigured packet stream L12020 can be transmitted througha data pipe and the extracted static chain can be transported throughout-of-band L12030.

A description will be given of a process of recovering an RoHC packetstream in a receiver according to an embodiment of the presentinvention.

The receiver according to an embodiment of the present invention canselect a data pipe corresponding to a packet stream to be received usingsignaling information. Then, the receiver can receive the packet streamtransmitted through the data pipe (S12040) and detect a static chaincorresponding to the packet stream. Here, the static chain can bereceived through out-of-band (S12050). Subsequently, the receiver candetect IR-DYN packets from the packet stream transmitted through thedata pipe. Then, the receiver can configure IR packets by combining thedetected IR-DYN packets with the static chain. The configured IR packetscan be transmitted to an RoHC decompressor. In addition, the receivercan configure an RoHC packet stream L12060 including the IR packets, theIR-DYN packets and/or general header compressed packets. The configuredRoHC packet stream can be transmitted to the RoHC decompressor. Thereceiver according to an embodiment of the present invention can recoverthe RoHC packet stream using the static chain, SNs and/or context IDs ofthe IR-DYN packets.

FIG. 28 shows combinations of information that can be transported out ofband according to an embodiment of the present invention.

According to an embodiment of the present invention, methods fortransporting a static chain and/or a dynamic chain, extracted in an RoHCpacket stream configuration process, out of band may include a methodfor transporting a static chain and/or a dynamic chain through signalingand a method for transporting a static chain and/or a dynamic chainthrough a data pipe through which parameters necessary for systemdecoding are delivered. In an embodiment of the present invention, thedata pipe through which parameters necessary for system decoding aredelivered may be called a base data pipe (DP).

As shown in the figure, the static chain and/or the dynamic chain can betransported through signaling or the base DP. In an embodiment of thepresent invention, transport mode #1, transport mode #2 and transportmode #3 can be used for configuration mode #1 or configuration mode #2and transport mode #4 and transport mode #5 can be used forconfiguration mode #3.

According to an embodiment of the present invention, the configurationmodes and the transport modes may be switched through additionalsignaling according to system state, and only one configuration mode andtransport mode can be fixed and used according to system design.

As shown in the figure, the static chain and the dynamic chain can betransmitted through signaling and a general header compressed packet canbe transmitted through a normal DP in transport mode #1.

Referring to the figure, the static chain can be transmitted throughsignaling, the dynamic chain can be transmitted through the base DP andthe general header compressed packet can be transmitted through a normalDP in transport mode #2.

As shown in the figure, the static chain and the dynamic chain can betransmitted through the base DP and the general header compressed packetcan be transmitted through a normal DP in transport mode #3.

Referring to the figure, the static chain can be transmitted throughsignaling, the dynamic chain can be transmitted through a normal DP andthe general header compressed packet can be transmitted through a normalDP in transport mode #4.

As shown in the figure, the static chain can be transmitted through thebase DP, the dynamic chain can be transmitted through a normal DP andthe general header compressed packet can be transmitted through a normalDP in transport mode #5. Here, the dynamic chain can be transmittedthrough an IR-DYN packet.

FIG. 29 illustrates a packet transmitted through a data pipe accordingto an embodiment of the present invention.

According to an embodiment of the present invention, it is possible togenerate a link layer packet which is compatible irrespective of changeof a protocol of an upper layer or a lower layer of the link layer bynewly defining a packet structure in the link layer.

The link layer packet according to an embodiment of the presentinvention can be transmitted through a normal DP and/or the base DP.

The link layer packet can include a fixed header, an extended headerand/or a payload.

The fixed header has a fixed size and the extended header has a sizevariable depending on a configuration of a packet of an upper layer. Thepayload is a region in which data of the upper layer is transmitted.

A packet header (fixed header or extended header) can include a fieldindicating the type of the payload of the packet. In the case of thefixed header, first 3 bits of 1 byte correspond to data indicating apacket type of the upper layer and the remaining 5 bits are used as anindicator part. The indicator part can include data indicating a payloadconfiguration method and/or configuration information of the extendedheader and the configuration of the indicator part can be changedaccording to packet type.

The figure shows types of packets of the upper layer, included in thepayload, according to packet type values.

The payload can carry an IP packet and/or an RoHC packet through a DPand carry a signaling packet through the base DP according to systemconfiguration. Accordingly, even when packets of various types aresimultaneously transmitted, a data packet and a signaling packet can bediscriminated from each other by assigning packet type values.

A packet type value of 000 indicates that an IP packet of IPv4 isincluded in the pay load.

A packet type value of 001 indicates that an IP packet of IPv6 isincluded in the payload.

A packet type value of 010 indicates that a compressed IP packet isincluded in the payload. The compressed IP packet may include aheader-compressed IP packet.

A packet type value of 110 indicates that a packet including signalingdata is included in the payload.

A packet type value of 111 indicates that a framed packet is included inthe payload.

FIG. 30 illustrates a syntax of a link layer packet structure accordingto an embodiment of the present invention.

FIG. 30 shows the structure of the aforementioned packet transmittedthrough a data pipe. The link layer packet may have a Packet_Type field.

A field following the Packet_Type field can depend on the value of thePacket_Type field. When the Packet_Type field has a value of 000 or 001,as shown in the figure, the Packet_Type field can be followed byLink_Layer_Packet_Header_for_IP( ), that is, a header structure for IPpackets. When the Packet_Type field has a value of 010,Link_Layer_Packet_Header_for_Compressed_IP( ), that is, a headerstructure for compressed IP packets can follow the Packet_Type field.When the Packet_Type field has a value of 011, the Packet_Type field canbe followed by Link_Layer_Packet_Header_for_TS( ) that is, a headerstructure for TS packets. When the Packet_Type field has a value of 110,Link_Layer_Packet_Header_for_Signaling( ), that is, a header structurefor signaling information can follow the Packet_Type field. When thePacket_Type field has a value of 111, the Packet_Type field can befollowed by Link_Layer_Packet_Header_for_Framed_Packet( ), that is, aheader structure for framed packets. Other values can be reserved forfuture use. Here, meaning of Packet_Type field values may be changedaccording to embodiments.

The field following the Packet_Type field can be followed byLink_Layer_Packet_Payload( ) which is a link layer packet payload.

FIG. 31 illustrates a link layer packet header structure when an IPpacket is delivered to the link layer according to another embodiment ofthe present invention.

In this case, the link layer packet header includes a fixed header andan extended header. The fixed header can have a length of 1 byte and theextended header can have a fixed length of a variable length. The lengthof each header can be changed according to design.

The fixed header can include a packet type field, a packet configuration(PC) field and/or a count field. According to another embodiment, thefixed header may include a packet type field, a PC field, an LI fieldand/or a segment ID field.

The extended header can include a segment sequence number field and/or asegment length ID field. According to another embodiment, the extendedfield may include a segment sequence number field and/or a last segmentlength field.

The fields of the fixed header will now be described.

The packet type field can indicate the type of a packet input to thelink layer, as described above. When an IP packet is input to the linklayer, the packet type field can have a value of 000B or 001B.

The PC field can indicate the remaining part of the fixed header, whichfollows the PC field, and/or the configuration of the extended header.That is, the PC field can indicate the form into which the input IPpacket has been processed. Accordingly, the PC field can includeinformation on the length of the extended header.

A PC field value of 0 can indicate that the payload of the link layerpacket includes one IP packet or two or more concatenated IP packets.Here, concatenation means that short packets are connected to form apayload.

When the PC field has a value of 0, the PC field can be followed by a4-bit count field. The count field can indicate the number ofconcatenated IP packets corresponding to one payload. The number ofconcatenated IP packets, indicated by the counter field, will bedescribed later.

When the PC field value is 0, the link layer may not include theextended header. However, when the length of the link layer packet needsto be indicated according to an embodiment, a one or two-byte extendedheader can be added. In this case, the extended header can be used toindicate the length of the link layer packet.

A PC field value of 1 can indicate that the link layer packet payloadincludes a segmented packet. Here, segmentation of a packet meanssegmentation of a long IP packet into a plurality of segments. Eachsegmented piece can be called a segment or a segmented packet. That is,when the PC field value is 1, the link layer packet payload can includeone segment.

When the PC field value is 1, the PC field can be followed by a 1-bitlast segment indicator (LI) field and a 3-bit segment ID field.

The LI field can indicate whether the corresponding link layer packetincludes the last segment from among segments. That is, thecorresponding link layer includes the last segment when the LI field hasa value of 1 and the corresponding link layer does not include the lastsegment when the LI field has a value of 0. The LI field can be usedwhen a receiver reconfigures the original IP packet. The LI field mayindicate information about the extended header of the link layer packet.That is, the length of the extended header can be 1 byte when the LIfield value is 0 and 2 bytes when the LI field value is 1. Details willbe described later.

The segment ID field can indicate the ID of a segment included in thecorresponding link layer packet. When one IP packet is segmented intosegments, the segments may be assigned the same ID. The segment IDenables the receiver to recognize that the segments are components ofthe same IP packet when reconfiguring the original IP packet. Since thesegment ID field has a size of 3 bits, segmentation of 8 IP packets canbe simultaneously supported.

When the PC field value is 1, the extended header can be used forinformation about segmentation. As described above, the extended headercan include the segment sequence number field, the segment length IDfield and/or the last segment length field.

The fields of the extended header will now be described.

When the aforementioned LI field has a value of 0, that is, when thelink layer packet does not include the last segment, the extended headercan include the segment sequence number field and/or the segment lengthID field.

The segment sequence number field can indicate sequence numbers ofsegmented packets. Accordingly, link layer packets having segmentsobtained by segmenting one IP packet have different segment sequencenumber fields while having the same segment ID field. Since the segmentsequence number field has a size of 4 bits, the IP packet can besegmented into a maximum of 16 segments.

The segment length ID field can indicate the length of segments otherthan the last segment. Segments other than the last segment may have thesame length. Accordingly, the length of the segments can be representedusing a predetermined length ID. The predetermined length ID can beindicated by the segment length ID field.

Segment lengths can be set according to a packet input size which isdetermined on the basis of an FEC code rate of the physical layer. Thatis, segment lengths can be determined according to the packet input sizeand designated by segment length IDs. To reduce header overhead, thenumber of segment lengths can be limited to 16.

Segment length ID field values according to segment lengths will bedescribed later.

When the physical layer operates irrespective of segment lengths, asegment length can be obtained by adding a minimum segment lengthmin_len to a product of the corresponding segment length ID and a lengthunit Len_Unit. Here, the length unit is a basic unit indicating asegment length and the minimum segment length means a minimum value ofthe segment length. The transmitter and the receiver need to always havethe same length unit and the same minimum segment length, and it isdesirable that the length unit and the minimum segment length not bechanged for efficient system operation. The length unit and the minimumsegment length can be determined in consideration of FEC processingcapability of the physical layer in the system initialization process.

When the aforementioned LI field has a value of 1, that is, when thelink layer packet includes the last segment, the extended header caninclude the segment sequence number field and/or the last segment lengthfield.

The segment sequence number field has been described above.

The last segment length field can directly indicate the length of thelast segment. When one IP packet is segmented into segments havingspecific lengths, the last segment may have a different length fromthose of other segments. Accordingly, the last segment length field candirectly indicate the length of the last segment. The last segmentlength field can represent 1 to 4095 bytes. Bytes indicated by the lastsegment length field may be changed according to embodiments.

FIG. 32 illustrates a syntax of a link layer packet header structurewhen an IP packet is delivered to the link layer according to anotherembodiment of the present invention.

The link layer packet header can include the Packet_Type field and thePC field Payload_Config, as described above.

When the PC field has a value of 0, the PC field can be followed by thecount field.

When the PC field has a value of 1, the PC field can be followed by aLast_Segment_ field, Segment_ID field and Segment_Sequence_Number field.Here, the configuration of the part following the Last_Segment_Indicatorfield can be changed according to the value of theLast_Segment_Indicator field. When the Last_Segment_Indicator field is0, the Segment_Length_ID field can follow the Segment_Sequence_Numberfield. When the Last_Segment_Indicator field is 1, theLast_Segment_Length field can follow the Segment_Sequence_Number field.

FIG. 33 illustrates indication of field values in a link layer packetheader when an IP packet is delivered to the link layer according toanother embodiment of the present invention.

As described above, the number of concatenated IP packets can bedetermined on the basis of a count field value (t61010). While the countfield value can directly indicate the number of concatenated IP packets,the count field value is meaningless when 0 packets are concatenated.Accordingly, the count field can indicate that as many IP packets as thevalue obtained by adding 1 to the count field value have beenconcatenated. That is, a count field value of 0010 can indicate that 3IP packets have been concatenated and a count field value of 0111 canindicate that 8 IP packets have been concatenated as shown in the tablet61010.

A count field value of 0000 indicating that one IP packet has beenconcatenated can represent that the link layer packet payload includesone IP packet without concatenation.

As described above, a segment length can be indicated by a segmentlength ID field value (t61020).

For example, a segment length ID field value of 0000 can indicate asegment length of 512 bytes. This means that a segment included in thecorresponding link layer packet payload is not the last segment and hasa length of 512 bytes. Other segments from the same IP packet may alsohave a length of 512 bytes if the segments are not the last segment.

In the table, the length unit has a value of 256 and the minimum segmentlength has a value of 512. Accordingly, the minimum segment length is512 bytes (segment length ID field=0000). Designated segment lengthsincrease at an interval of 256 bytes.

FIG. 34 illustrates a case in which one IP packet is included in a linklayer payload in a link layer packet header structure when IP packetsare delivered to the link layer according to another embodiment of thepresent invention.

A case in which one IP packet is included in the link layer payload,that is, a case in which concatenation or segmentation is not performedmay be referred to as encapsulation into a normal packet. In this case,the IP packet is within a processing range of the physical layer.

In the present embodiment, the link layer packet has a 1-byte header.The header length may be changed according to embodiments. The packettype field may have a value of 000 (in the case of IPv4) or 001 (in thecase of IPv6). Normal packet encapsulation can be equally applied toIPv4 and IPv6. The PC field value can be 0 since one packet is includedin the payload. The count field following the PC field can have a valueof 0000 since only one packet is included in the payload.

In the present embodiment, the link layer packet payload can include onewhole IP packet.

In the present embodiment, information of the IP packet header can beused to confirm the length of the link layer packet. The IP packetheader includes a field indicating the length of the IP packet. Thisfield can be called a length field. The length field may be located at afixed position in the IP packet. Since the link layer payload includesone whole IP packet, the length field can be located at a position at adistance from the starting point of the link layer packet payload by apredetermined offset. Accordingly, the length of the link layer payloadcan be recognized using the length field.

The length field can be located at a position at a distance from thestarting point of the payload by 4 bytes in the case of IPv4 and at aposition at a distance from the starting point of the payload by 2 bytesin the case of IPv6. The length field can have a length of 2 bytes.

In the case of IPv4, when the length field value is LIPv4 and the linklayer packet header length is LH (1 byte), the total length of the linklayer packet, LT, can be represented by an equation t62010 shown in thefigure. Here, the length field value LIPv4 can indicate the length ofthe IPv4 packet.

In the case of IPv6, when the length field value is LIPv6 and the linklayer packet header length is LH (1 byte), the total link layer packetlength LT can be represented by an equation t62020 shown in the figure.Here, since the length field value LIPv6 indicates only the length ofthe IPv6 packet payload, the length (40 bytes) of the fixed header ofthe IPv6 packet needs to be added to the length field value in order toobtain the length of the link layer packet.

FIG. 35 illustrates a case in which multiple IP packets are concatenatedand included in a link layer payload in a link layer packet headerstructure when IP packets are delivered to the link layer according toanother embodiment of the present invention.

When input IP packets are not within the processing range of thephysical layer, multiple IP packets may be concatenated and encapsulatedinto a payload of one link layer packet.

In the present embodiment, the link layer packet can have a 1-byteheader. The header length may be changed according to embodiments. Thepacket type field can have a value of 000 (in the case of IPv4) or 001(in the case of IPv6). The encapsulation process of the presentembodiment can be equally applied to IPv4 and IPv6. The PC field valuecan be 0 since the concatenated IP packets are included in the payload.The count field following the PC field (4 bits) can indicate the numberof concatenated IP packets.

In the present embodiment, the link layer packet payload can includemultiple IP packets. The multiple IP packets can be sequentiallyconcatenated and included in the link layer packet payload. Theconcatenation method can be changed according to design.

In the present embodiment, to confirm the length of the link layerpacket, information of headers of the concatenated IP packets can beused. As in the aforementioned normal packet encapsulation, the headerof each IP packet may have the length field indicating the length of theIP packet. The length field can be located at a fixed position in thecorresponding IP packet.

Accordingly, when the header length of the link layer packet is LH andthe length of each IP packet is LK (K being equal to or greater than 1and equal to or less than n), the total length of the link layer packetlength, LT, can be represented by an equation t63010 shown in thefigure. That is, the link layer packet length can be obtained by summingthe lengths of the IP packets, respectively indicated by the lengthfields of the IP packets, and adding the header length of the link layerpacket to the sum. LK can be confirmed by reading the length fields ofthe headers of the respective IP packets.

FIG. 36 illustrates a case in which one IP packet is segmented andincluded in a link layer payload in a link layer packet header structurewhen IP packets are delivered to the link layer according to anotherembodiment of the present invention.

When input IP packets exceed the processing range of the physical layer,one IP packet may be segmented into a plurality of segments. Thesegments can be respectively encapsulated in payloads of link layerpackets.

In the present embodiment, link layer packets t64010, t64020 and t64030can have fixed headers and extended headers. The fixed header length andextended header length may be changed according to embodiments. Thepacket type field value can be 000 (in the case of IPv4) or 001 (in thecase of IPv6). The encapsulation process of the present embodiment canbe equally applied to IPv4 and IPv6. The PC field value can be 1 sincethe segments are included in the payloads.

The link layer packets t64010 and t64020 including segments, which arenot the last segment, in the payloads thereof can have an LI field valueof 0 and the same segment ID field value since the segments are from thesame IP packet. The segment sequence number field following the segmentID field can indicate the sequence of the corresponding segment. Here,the segment sequence field value of the first link layer packet t64010can indicate that the link layer packet has the first segment as apayload. The segment sequence field value of the second link layerpacket t64020 can indicate that the link layer packet has the secondsegment as a payload. The segment length ID field can represent thelength of the corresponding segment as a predetermined length ID.

The link layer packet t64030 having the last segment as a payload mayhave an LI field value of 1. The segment ID field can have the samevalue as those of other link layer packets since the last segment isalso from the same IP packet. The segment sequence number fieldfollowing the segment ID field can indicate the sequence of thecorresponding segment. The last segment length field can directlyindicate the length of the last segment included in the link layerpacket t64030.

In the present embodiment, to confirm the length of a link layer packet,the segment length ID field or the last segment length field can beused. Since the fields indicate only the length of the payload of thelink layer packet, the header length of the link layer packet needs tobe added thereto in order to obtain the length of the link layer packet.The header length of the link layer packet can be detected from the LIfield, as described above.

FIG. 37 illustrates link layer packets having segments in a link layerpacket header structure when IP packets are transmitted to the linklayer according to another embodiment of the present invention.

The present embodiment assumes that a 5500-byte IP packet is input.Since the value obtained by dividing 5500 by 5 is 1100, the IP packetcan be segmented into segments each having a length of 1024 bytes closesto 1100. In this case, the last segment can be 1404 bytes(010101111100B). The segments can be respectively referred to as S1, S2,S3, S4 and S5 and headers corresponding thereto can be respectivelyreferred to as H1, H2, H3, H4 and H5. The headers can be respectivelyadded to the segments to generate respective link layer packets.

When the input IP packet is an IPv4 packet, the packet type fields ofthe headers H1 to H5 can have a value of 000. The PC fields of theheaders H1 to H5 can have a value of 1 since the link layer packets havethe segments of the packet as payloads.

LI fields of the headers H1 to H4 can have a value of 0 since thecorresponding link layer packets do not have the last segment as apayload. The LI field of the header H5 can have a value of 1 since thecorresponding link layer packet has the last segment as a payload. Thesegment ID fields, Seg_ID, of the headers H1 to H5 can have the samevalue, 000, since the corresponding link layer packets have segmentsfrom the same packet as payloads.

The segment sequence number fields, Seg_SN, of the headers H1 to H5 canbe sequentially represented as 0000B to 0100B. The segment length IDfields of the headers HI to H4 can have a value of 0010 corresponding toan ID that is 1024 bytes in length. The segment length ID field of theheader H5 can have a value of 010101111100 which indicates 1404 bytes.

FIG. 38 illustrates a header of a link layer packet for RoHCtransmission according to an embodiment of the present invention.

Even in an IP based broadcast environment, an IP packet can becompressed into a link layer packet and transmitted. When an IP basedbroadcast system streams IP packets, header information of the IPpackets can generally remain unchanged. Using this fact, IP packetheaders can be compressed.

Robust header compression (RoHC) is mainly used to compress an IP packetheader (IP header). The present invention proposes an encapsulationmethod when RoHC packets are input to the link layer.

When RoHC packets are input to the link layer, the aforementioned packettype element may have a value of 010B, which indicates that a packetdelivered from an upper layer to the link layer is a compressed IPpacket.

When RoHC packets are input, the header of the link layer packet caninclude a fixed header and/or an extended header like the aforementionedother packets.

The fixed header can include a packet type field and/or a packetconfiguration (PC) field. The fixed header may have a size of 1 byte.Here, the packet type field can have a value of 010 since the inputpacket is a compressed IP packet. The extended header can have a fixedsize or a variable size according to embodiments.

The PC field of the fixed header can indicate a form into which RoHCpackets constituting the link layer packet payload are processed.Information of the remaining part of the fixed header, which follows thePC field, and the extended header can be determined by the value of thePC field. In addition, the PC field can include information on thelength of the extended header according to the form into which RoHCpackets are processed. The PC field can have a size of 1 bit.

A description will be given of a case in which the PC field has a valueof 0B.

When the PC field has a value of 0B, the link layer packet payload iscomposed of one RoHC packet or two or more concatenated RoHC packets.Concatenation refers to connecting a plurality of short packets toconfigure a link layer packet payload.

When the PC field has a value of 0B, the PC field can be followed by a1-bit common context ID indicator (CI) field and a 3-bit count field.Accordingly, common CID information and a length part can be added tothe extended header. The length part can indicate the length of an RoHCpacket.

The CI field can be set to 1 when RoHC packets constituting the payloadof one link layer packet have the same context ID (CID) and set to 0otherwise. When the CI field has a value of 1, an overhead processingmethod for a common CID can be applied. The CI field can be 1 bit.

The count field can indicate the number of RoHC packets included in thepayload of one link layer packet. That is, when RoHC packets areconcatenated, the number of concatenated RoHC packets can be indicatedby the count field. The count filed can be 3 bits. Accordingly, amaximum of 8 RoHC packets can be included in the payload of one linklayer packet, as shown in the following table. A count field value of000 indicates that the link layer packet payload is composed of one RoHCpacket rather than multiple concatenated RoHC packets.

TABLE 1 Count (3 bits) No. of Concatenated RoHC packets 000 1 001 2 0103 011 4 100 5 101 6 110 7 111 8

The length part can indicate an RoHC packet length, as described above.The RoHC packet has a header from which length information has beenremoved, and thus the length field in the RoHC packet header cannot beused. Accordingly, the header of the link layer packet can include thelength part in order to enable the receiver to recognize the length ofthe corresponding RoHC packet.

An IP packet has a maximum of 65535-byte length when an MTU is notdetermined. Accordingly, 2-byte length information is necessary for theRoHC packet such that a maximum length thereof can be supported. Whenmultiple RoHC packets are concatenated, as many length fields as thenumber designated by the count field can be added. In this case, thelength part includes a plurality of length fields. However, when oneRoHC packet is included in the payload, only one length field can beincluded in the length part. Length fields can be arranged in the sameorder as that of RoHC packets constituting the link layer packetpayload. Each length field can be a value in bytes.

A common CID field is a field through which a common CID is transmitted.The header of the RoHC packet may include a context ID (CID) used tocheck the relation between compressed headers. The CID can be maintainedas the same value in a stable link state. Accordingly, all RoHC packetsincluded in the payload of one link layer packet may include the sameCID. In this case, to reduce overhead, it is possible to remove the CIDfrom the headers of concatenated RoHC packets constituting the payload,indicate the CID in the common CID field of the header of the link layerpacket and transmit the link layer packet. The receiver can reconfigurethe CID of the RoHC packets using the common CID field. When the commonCID field is present, the aforementioned CI field needs to have a valueof 1.

A description will be given of a case in which the PC field has a valueof 1B.

A PC field value of 1B indicates that a link layer packet payload iscomposed of segmented packets of an RoHC packet. Here, a segmentedpacket refers to a segment from among a plurality of segments obtainedby segmenting a long RoHC packet. One segment constitutes a link layerpacket payload.

When the PC field has a value of 1B, the PC field can be followed by a1-bit last segment indicator (LI) field and a 3-bit segment ID field. Toadd information about segmentation, a segment sequence number field, asegment length ID field and a last segment length field may be added tothe extended header.

The LI field can be used when an RoHC packet is segmented. An RoHCpacket can be segmented into a plurality of segments. An LI field valueof 1 can indicate that a segment included in the current link layerpacket is the last segment from among segments obtained from one RoHCpacket. An LI field value of 0 can indicate that a segment included inthe current link layer packet is not the last segment. The LI field canbe used when the receiver determines whether all segments have beenreceived when reconfiguring one RoHC packet by combining segments. TheLI field can be 1 bit.

The segment ID field Seg_ID can indicate an ID assigned to an RoHCpacket when the RoHC packet is segmented. Segments derived from one RoHCpacket can have the same segment ID. The receiver can determine whethersegments transmitted thereto are components of the same RoHC packetusing the segment ID when combining the segments. The segment ID fieldcan be 3 bits. Accordingly, the segment ID field can simultaneouslysupport segmentation of 8 RoHC packets.

The segment sequence number field Seg_SN can be used to check thesequence of segments when an RoHC packet is segmented. That is, linklayer packets having segments derived from one RoHC packet as payloadthereof may have different segment sequence number fields while havingthe same sequence ID field. Accordingly, one RoHC packet can besegmented into a maximum of 16 segments.

The segment length ID field Seg_Len_ID can be used to represent thelength of each segment. However, the segment length ID field can be usedto indicate the length of segments other than the last segment fromamong a plurality of segments. The length of the last segment can beindicated by the last segment length field which will be describedlater. When a link layer packet payload does not correspond to the lastsegment of an RoHC packet, that is, when the LI field is 0, the segmentlength ID field can be present.

To reduce header overhead, the number of segment lengths can be limitedto 16. A packet input size may be determined according to code rate ofFEC processed in the physical layer. Segment lengths can be determinedaccording to the packet input size and designated by Seg_Len_ID. Whenthe physical layer operates irrespective of segment lengths, a segmentlength can be determined as follows.Segment Length=Seg_Len_ID×Len_Unit+min_Len[bytes]  [Equation 1]

Here, a length unit Len_Unit is a basic unit indicating a segment lengthand min_Len indicates a minimum segment length. The transmitter and thereceiver need to have the same Len_Unit and the same min_Len. It isefficient for system operation that Len_Unit and the same min_Len arenot changed after being determined once. Furthermore, Len_Unit andmin_Len can be determined in consideration of FEC processing capabilityof the physical layer in the system initialization process.

The following table shows segment lengths represented according toSeg_Len_ID values. A length allocated to Seg_Len_ID can be changedaccording to design. In the present embodiment, Len_Unit is 256 andmin_Len is 512.

TABLE 2 Seg_Len_ID Segment Length (byte) 0000 512 (=min_Len) 0001  7680010 1024 0011 1280 0100 1536 0101 1792 0110 2048 0111 2304 1000 25601001 2816 1010 3072 1011 3328 1100 3584 1101 3840 1110 4096 1111 4352

The last segment length field L_Seg_Len is used when a segment includedin a link layer packet payload is the last segment of the correspondingRoHC packet. That is, the last segment length field is used when the LIfield has a value of 1. An RoHC packet can be segmented into segments ofthe same size using Seg_Len_ID. In this case, however, the last segmentmay not have the size indicated by Seg_Len_ID. Accordingly, the lengthof the last segment can be directly indicated by the last segment lengthfield. The last segment length field can indicate 1 to 4095 bytes. Thiscan be changed according to embodiments.

FIG. 39 illustrates a syntax of a header of a link layer packet for RoHCpacket transmission according to an embodiment of the present invention.

The link layer packet header may include the Packet_Type field and thePC field Payload_Config, which have been described above.

When the PC field has a value of 0, the PC field can be followed by aCommon_Context_ID_Indication field and a count field. A plurality oflength fields can be included in the link layer packet on the basis of avalue indicated by the count field. When the CI field is 1, a Common_CIDfield can be additionally included in the link layer packet header.

When the PC field is 1, the PC field can be followed by aLast_Segment_Indicator field, a Segment_ID field and aSegment_Sequence_Number field. A configuration of the part following theLast_Segment_Indicator field can be changed according to the value ofthe Last_Segment_Indicator field. When the Last_Segment_Indicator fieldis 0, the Segment_Sequence_Number field can be followed by theSegment_Length_ID field. When the Last_Segment_Indicator field is 1, theSegment_Sequence_Number field can be followed by the Last_Segment_Lengthfield.

FIG. 40 illustrates a method for transmitting an RoHC packet through alink layer packet according to embodiment #1 of the present invention.

The present embodiment corresponds to a case in which one RoHC packetconstitutes a link layer packet payload since the RoHC packet is withina processing range of the physical layer. Here, the RoHC packet may notbe concatenated or segmented.

In this case, one RoHC packet can become a link layer packet payload.The packet type field can be 010B, the PC field can be 0B and the CIfield can be 0B. The aforementioned count field can be 000B since oneRoHC packet constitutes the payload (the number of RoHC packetsconstituting the payload being 1). The count field can be followed by a2-byte length field indicating the length of the RoHC packet. In thiscase, the length part can include only one length field since only onepacket constitutes the payload.

In the present embodiment, a 3-byte link layer header can be added.Accordingly, when the length of the RoHC packet, indicated by the lengthfield, is L bytes, the length of the link layer packet is L+3 bytes.

FIG. 41 illustrates a method for transmitting an RoHC packet through alink layer packet according to embodiment #2 of the present invention.

The present embodiment corresponds to a case in which an RoHC packetdoes not exceed the processing range of the physical layer and thusmultiple RoHC packets are concatenated and included in a payload of alink layer packet.

In this case, the PC field and the CI field have same values as those ina case in which one RoHC packet is included in a link layer packetpayload. The CI field is followed by the count field. The count fieldcan have a value in the range of 001B to 111B on the basis of the numberof RoHC packets included in the payload, as described above.

The count field can be followed by as many 2-byte length fields as thenumber indicated by the count field. Each length field can indicate thelength of each RoHC packet. The length fields can be called a lengthpart.

When the count field indicates n, RoHC packets R1, R2, . . . , Rnrespectively having lengths L1, L2, . . . , Ln can be concatenated inthe link layer packet payload.

The extended header can have a length of 2n bytes. The total length ofthe link layer packet, LT, can be represented by the following equation.

$\begin{matrix}\begin{matrix}{L_{T} = {1 + {2n} + {\sum\limits_{k = 1}^{n}L_{k}}}} & \lbrack{bytes}\rbrack\end{matrix} & \left\lbrack {{Equation}\mspace{14mu} 2} \right\rbrack\end{matrix}$

FIG. 42 illustrates a method for transmitting an RoHC packet through alink layer packet according to embodiment #3 of the present invention.

The present embodiment corresponds to a case in which RoHC packets areconcatenated to constitute a payload of a link layer packet and the RoHCpackets have the same CID.

When the RoHC packets have the same CID, even if the CID is indicatedonly once through the link layer packet and transmitted to the receiver,the receiver can recover the original RoHC packets and headers thereof.Accordingly, a common CID can be extracted from the RoHC packets andtransmitted, reducing overhead.

In this case, the aforementioned CI field becomes 1, which representsthat processing for the same CID has been performed. The RoHC packetshaving the same CID are indicated by [R1, R2, R3, . . . , Rn]. The sameCID is referred to as a common CID. Packets other than CIDs in RoHCpacket headers are referred to as R′k (k being 1, 2, . . . , n).

The link layer packet payload can include R′k (k being 1, 2, . . . , n).A common CID field can be added to the end of the extended header of thelink layer packet. The common CID field may be a field for common CIDtransmission. The common CID field may be transmitted as a part of theextended header or a part of the link layer packet payload. It ispossible to rearrange the common CID field in a part in which theposition of the common CID field can be identified according to systemoperation.

The size of the common CID field can depend on RoHC packetconfiguration.

When the RoHC packet configuration is a small CID configuration, the CIDof an RoHC packet can be 4 bits. However, when the CID is extracted fromthe RoHC packet and rearranged, the entire add-CID octet can beprocessed. That is, the common CID field can have a length of 1 byte.Alternatively, it is possible to extract a 1-byte add-CID octet from theRoHC packet, allocate only a 4-bit CID to the common CID field andreserve the remaining 4 bits for future use.

When the RoHC packet configuration is a large CID configuration, the CIDof an RoHC packet can be 1 byte or 2 bytes. The CID size is determinedin the RoHC initialization process. The common CID field can have alength of 1 byte or 2 bytes depending on the CID size.

In the present embodiment, the link layer packet payload can becalculated as follows. n RoHC packets R1, R2, Rn having the same CID arerespectively referred to as L1, L2, . . . , Ln. When the length of thelink layer packet header is LH, the length of the common CID field isLCID and the total length of the link layer packet is LT, LH iscalculated as follows.L _(H)=1+2n+L _(CID) bytes  [Equation 3]

LT can be calculated as follows.

$\begin{matrix}\begin{matrix}{L_{T} = {L_{H} + {\sum\limits_{k = 1}^{n}\left( {L_{k} - L_{CID}} \right)}}} & {bytes}\end{matrix} & \left\lbrack {{Equation}\mspace{14mu} 4} \right\rbrack\end{matrix}$

As described above, LCID can be determined according to CIDconfiguration of RoHC. That is, LCID can be 1 byte in the case of asmall CID configuration and 1 byte or 2 bytes in the case of a large CIDconfiguration.

FIG. 43 illustrates a method for transmitting an RoHC packet through alink layer packet according to embodiment #4 of the present invention.

The present embodiment corresponds to a case in which an input RoHCpacket exceeds the processing range of the physical layer and thus theRoHC packet is segmented and the segments of the RoHC packet arerespectively encapsulated into link layer packet payloads.

To indicate that the link layer packet payloads are composed ofsegmented RoHC packets, the PC field can be 1B. The LI field becomes 1Bonly in a link layer packet having the last segment of the RoHC packetas a payload and becomes 0B for the remaining segments. The LI fieldalso indicates information about the extended header of thecorresponding link layer packet. That is, a 1-byte extended header canbe added when the LI field is 0B and a 2-byte extended header can beadded when the LI field is 1B.

The link layer packets need to have the same Seg_ID value in order toindicate that the segments have been derived from the same RoHC packet.To indicate the order of segments for normal RoHC packet reconfigurationin the receiver, a sequentially increasing Seg_SN value can be includedin corresponding headers.

When the RoHC packet is segmented, a segment length can be determined,as described above, and segmentation can be performed. A Seg_Len_IDvalue corresponding to the segment length can be included in thecorresponding headers. The length of the last segment can be directlyincluded in a 12-bit L_Seg_Len field, as described above.

Length information indicated using the Seg_Len_ID and L_Seg_Len fieldsrepresents only information about a segment, that is, a payload of alink layer packet. Accordingly, the total length of the link layerpacket can be calculated by adding the header length of the link layerpacket, which can be detected from the LI field, to the length of thelink layer packet payload.

When the receiver reconfigures the segments of the RoHC packet, it isnecessary to check integrity of the reconfigured RoHC packet. To thisend, a CRC can be added to the end of the RoHC packet in a segmentationprocess. Since the CRC is generally added to the end of the RoHC packet,the CRC can be included in the segment after segmentation.

FIG. 44 illustrates a link layer packet structure when signalinginformation is delivered to the link layer according to anotherembodiment of the present invention.

In this case, the header of the link layer packet can include a fixedheader and an extended header. The fixed header can have a length of 1byte and the extended header can have a fixed length or a variablelength. The length of each header can be changed according to design.

The fixed header can include a packet type field, a PC field and/or aconcatenation count field. According to another embodiment, the fixedheader may include the packet type field, the PC field, an LI fieldand/or a segment ID field.

The extended header can include a signaling class field, an informationtype field and/or a signaling format field. According to anotherembodiment, the extended header may further include a payload lengthpart. According to another embodiment, the extended header may include asegment sequence number field, a segment length ID field, the signalingclass field, the information type field and/or the signaling formatfield. According to another embodiment, the extended header may includethe segment sequence number field and/or the segment length ID field.According to another embodiment, the extended header may include thesegment sequence number field and/or a last segment length field.

The fields of the fixed header will now be described.

The packet type field can indicate the type of a packet input to thelink layer, as described above. When signaling information is input tothe link layer, the packet type field can be 110B.

The PC field, the LI field, the segment ID field, the segment sequencenumber field, the segment length ID field and the last segment field areas described above. The concatenation count field is as described above.

Description will be given of the fields of the extended header.

When the PC field is 0, the extended header can include the signalingclass field, the information type field and/or the signaling formatfield. The extended header may further include a length part accordingto the value of the signaling format field.

The signaling class field can indicate the type of signaling informationincluded in the link layer packet. Signaling information that can beindicated by the signaling class field can include fast informationchannel (FIC) information, header compression information and the like.The signaling information that can be indicated by the signaling classfield will be described later.

The information type field can indicate details of signaling informationof the type indicated by the signaling class field. Indication of theinformation type field can be separately defined according to the valueof the signaling class field.

The signaling format field can indicate a format of signalinginformation included in the link layer packet. Formats that can beindicated by the signaling format field may include a section table, adescriptor, XML and the like. The formats that can be indicated by thesignaling format field will be described later.

A payload length part can indicate the length of signaling informationincluded in the payload of the link layer packet payload. The payloadlength part may be a set of length fields respectively indicatinglengths of concatenated signaling information. While each length fieldmay have a size of 2 bytes, the size can be changed according to systemconfiguration. The total length of the payload length part can berepresented by the sum of the respective length fields. A padding bitfor byte arrangement can be added to the payload length part accordingto an embodiment. In this case, the total length of the payload lengthpart can increase by the padding bit.

Presence or absence of the payload length part can be determined by thesignaling format field value. When signaling information has a lengthvalue thereof, such as the section table and descriptor, an additionallength field may not be needed. However, signaling information having nolength value may require an additional length field. In the case ofsignaling information having no length value, the payload length partcan be present. In this case, the payload length part can include asmany length fields as the number of count fields.

When the PC field is 1 and the LI field is 1, the extended header caninclude the segment sequence number field and/or the last segment lengthfield. When the PC field is 1 and the LI field is 0, the extended headercan include the segment sequence number field and/or the segment lengthID field.

The segment sequence number field, the last segment length field and thesegment length ID field are as described above.

When the PC field is 1, the LI field is 1 and the payload of thecorresponding link layer packet corresponds to the first segment, theextended header of the link layer packet can further include additionalinformation. The additional information can include the signaling classfield, the information type field and/or the signaling format field. Thesignaling class field, the information type field and the signalingformat field are as described above.

FIG. 45 illustrates a syntax of a link layer packet structure whensignaling information is delivered to the link layer according toanother embodiment of the present invention.

The link layer packet header can include the Packet_Type field and thePC field Payload_Config, as described above.

When the PC field is 0, the PC field can be followed by a Count field, aSignaling_Class field, an Information_Type field and a Signaling_Formatfield. When the Signaling_Format field is 1x (10 or 11), a plurality oflength fields can be included in the link layer packet header on thebasis of a value indicated by the count field.

When the PC field is 1, the PC field can be followed by aLast_Segment_Indicator field, a Segment_ID field and aSegment_Sequence_Number field. Here, a configuration of a part followingthe Last_Segment_Indicator field can be changed according to the valueof the Last_Segment_Indicator field.

When the Last_Segment_Indicator field is 0, the Segment_Sequence_Numberfield can be followed by the Segment_Length_ID field. When theSegment_Sequence_Number field is 0000, the Segment_Sequence_Number fieldcan be followed by the Signaling_Class field, the Information Type fieldand the Signaling_Format field.

When the Last_Segment_Indicator field is 1, the Segment_Sequence_Numberfield can be followed by the Last_Segment_Length field.

FIG. 46 illustrates a structure of a link layer packet for framed packettransmission according to an embodiment of the present invention.

Packets used in normal networks, other than the IP packet and MPEG-2 TSpacket, can be transmitted through a link layer packet. In this case,the packet type element of the header of the link layer packet can havea value of 111B to indicate that the payload of the link layer packetincludes a framed packet.

FIG. 47 illustrates a syntax of a structure of a link layer packet forframed packet transmission according to an embodiment of the presentinvention.

The link layer packet header can include the Packet Type field, asdescribed above. The link layer packet header can include 5 bitsreserved for future use after the Packlet_Type field. A framed packetindicated by framed_packet( ) can follow the reserved bits.

FIG. 48 illustrates a syntax of a framed packet according to anembodiment of the present invention.

The syntax of the framed packet can include an Ethernet_type field, alength field, and/or a packet( ) field. The Ethernet_type field, whichis 16 bits, can indicate the type of a packet in the packet( ) fieldaccording to IANA registry. Here, only registered values can be used.The length field, which is 16 bits, can set the total length of thepacket structure in bytes. The packet( ) field having a variable lengthcan include a network packet.

FIG. 49 illustrates a syntax of a fast information channel (FIC)according to an embodiment of the present invention.

Information included in the FIC can be transmitted in the form of a fastinformation table (FIT).

Information included in the FIT can be transmitted in the form of XMLand/or a section table.

The FIC can include FIT_data_version information, num_broadcastinformation, broadcast_id information, delivery_system_id information,base_DP_id information, base_DP_version information, num_serviceinformation, service_id information, service_category information,service_hidden_flag information, SP_indicator information, num_componentinformation, component_id information, DP_id information and/orRoHC_init_descriptor information.

The FIT_data_version information can indicate version information abouta syntax and semantics included in the fast information table. Thereceiver can determine whether to process signaling included in the fastinformation table using the FIT_data_version information. The receivercan determine whether to update prestored information of the FIC usingthe FIT_data_version information.

The num_broadcast information can indicate the number of broadcastingstations which transmit broadcast services and/or content throughcorresponding frequencies or transmitted transport frames.

The broadcast_id information can indicate identifies of broadcastingstations which transmit broadcast services and/or content throughcorresponding frequencies or transmitted transport frames. Abroadcasting station transmitting MPEG-2 TS based data may have abroadcast_id identical to a transport_stream_id of an MPEG-2 TS.

The delivery_system_id information can indicate an identifier of abroadcast transmission system which performs processing using the sametransmission parameter on a broadcast network.

The base DP_id information indicates a base DP in a broadcast signal.The base DP can refer to a DP conveying service signaling includingprogram specific information (PSI)/system information (SI) and/oroverhead reduction of a broadcasting station corresponding to thebroadcast_id. Otherwise, the base DP can refer to a representative DPwhich can be used to decode components constituting broadcast servicesin the corresponding broadcasting station.

The base_DP_version information can indicate version information aboutdata transmitted through the base DP. For example, when servicesignaling such as PSI/IS through the base DP, the value of thebase_DP_version information can increase by 1 if service signalingchanges.

The num_service information can indicate the number of broadcastservices transmitted by the broadcasting station corresponding to thebroadcast_id in the corresponding frequency or transport frame.

The service_id information can be used as an identifier of a broadcastservice.

The service_category information can indicate a broadcast servicecategory. A service_category information value of 0x01 can indicateBasic TV, a service_category information value of 0x02 can indicateBasic Radio, a service_category information value of 0x03 can indicateRI service, a service_category information value of 0x08 can indicateService Guide, and a service_category information value of 0x09 canindicate Emergency Alerting.

The service_hidden_flag information can indicate whether thecorresponding broadcast service is hidden. When the broadcast service ishidden, the broadcast service is a test service or a serviceautonomously used in the corresponding system and thus a broadcastreceiver can ignore the service or hide the same in a service list.

The SP_indicator information can indicate whether service protection isapplied to one or more components in the corresponding broadcastservice.

The num_component information can indicate the number of componentsconstituting the corresponding broadcast service.

The component_id information can be used as an identifier foridentifying the corresponding component in the broadcast service.

The DP_id information can be used as an identifier indicating a DPthrough which the corresponding component is transmitted.

The RoHC_init_descriptor can include information related to overheadreduction and/or header recovery. The RoHC_init_descriptor can includeinformation for identifying a header compression method used at atransmitting end.

FIG. 50 illustrates a broadcast system issuing an emergency alertaccording to an embodiment of the present invention.

Upon reception of information related to an emergency alert from analert authority/originator, a broadcasting station (transmitter)converts the information related to the emergency alert into emergencyalert signaling in a format adapted to a broadcast system or generatesemergency alert signaling including the information related to theemergency alert. In this case, the emergency alert signaling may includea common alerting protocol (CAP) message. The broadcasting station cantransmit the emergency alert signaling to a receiver. Here, thebroadcasting station can transmit the emergency alert signaling througha path through which normal broadcast data is delivered. Otherwise, thebroadcasting station may transmit the emergency alert signaling througha path different from the path through which normal broadcast data isdelivered. The emergency alert signaling may be generated in the form ofan emergency alert table (EAT) which will be described later.

The receiver receives the emergency alert signaling. An emergency alertsignaling decoder can parse the emergency alert signaling to obtain theCAP message. The receiver generates an emergency alert message usinginformation of the CAP message and displays the emergency alert message.

FIG. 51 illustrates a syntax of an emergency alert table (EAT) accordingto an embodiment of the present invention.

Information related to an emergency alert can be transmitted through anEAC. The EAC corresponds to the aforementioned dedicated channel.

The EAT according to an embodiment of the present invention may includeEAT_protocol_version information, automatic_tuning_flag information,num_EAS_messages information, EAS_message_id information,EAS_IP_version_flag information, EAS_message_transfer_type information,EAS_message_encoding_type information, EAS_NRT_flag information,EAS_message_length information, EAS_message_byte information, IP_addressinformation, UDP_port_num information, DP_id information,automatic_tuning_channel_number information, automatic_tuning_DP_idinformation, automatic_tuning_service_id information and/orEAS_NRT_service_id information.

The EAT_protocol_version information indicates a protocol versioncorresponding to the received EAT.

The automatic_tuning_flag information indicates whether the receiverautomatically performs channel tuning.

The num_EAS_messages information indicates the number of messagesincluded in the EAT.

The EAS_message_id information identifies each EAS message.

The EAS_IP_version_flag information indicates IPv4 when theEAS_IP_version_flag information has a value of 0 and indicates IPv6 whenthe EAS_IP_version information has a value of 1.

The EAS_message_transfer_type information indicates an EAS messagetransfer type. The EAS_message_transfer_type information indicates “notspecified” when the EAS_message_transfer_type information is 000,indicates “no alert message (only AV content)” when theEAS_message_transfer_type information is 001 and indicates that thecorresponding EAT includes an EAS message when theAS_message_transfer_type information is 010, To this end, a length fieldand a field with respect to the corresponding EAS message are added.When the EAS_message_transfer_type information is 011, this informationindicates that the corresponding EAS message is transmitted through adata pipe. The EAS can be transmitted in the form of an IP datagramwithin the data pipe. To this end, IP address information, UDP portinformation and DP information of a physical layer to which the EASmessage is transmitted may be added.

The EAS_message_encoding_type information indicates information aboutencoding type of an emergency alert message. For example, anEAS_message_encoding_type information value of 000 can indicate “notspecified”, an EAS_message_encoding_type information value of 001 canindicate “no encoding”, an EAS_message_encoding_type information valueof 010 can indicate DEFLATE algorithm (RFC1951) andEAS_message_encoding_type information values of 011 to 111 can bereserved for other encoding types.

The EAS_NRT_flag information indicates presence or absence of NRTcontent and/or NRT data related to a received message. An EAS_NRT_flaginformation value of 0 indicates absence of NRT content and/or NRT datarelated to a received emergency message, whereas and an EAS_NRT_flaginformation value of 1 indicates presence of NRT content and/or NRT datarelated to the received emergency message.

The EAS_message_length information indicates the length of an EASmessage.

The EAS_message_byte information includes content of the EAS message.

The IP_address information indicates the IP address of an IP packetcarrying the EAS message.

The UDP_port_num information indicates the number of a UDP port throughwhich the EAS message is transmitted.

The DP_id information identifies a data pipe through which the EASmessage is transmitted.

The automatic_tuning_channel_number information includes informationabout the number of a channel to be tuned to.

The automatic_tuning_DP_id information identifies a data pipe throughwhich corresponding content is transmitted.

The automatic_tuning_service_id information identifies a service towhich the corresponding content belongs.

The EAS NRT_service_id information identifies an NRT servicecorresponding to a case in which NRT content and data related to areceived emergency alert message are transmitted, that is, when theEAS_NRT_flag is enabled.

FIG. 52 illustrates a method for identifying information related toheader compression, which is included in a payload of a link layerpacket according to an embodiment of the present invention.

When header compression is performed on a packet delivered from the linklayer to an upper layer, as described above, necessary information needsto be generated in a signaling form and transmitted to the receiver suchthat the receiver can recover the header of the packet. Such informationcan be referred to as header compression signaling information.

The header compression signaling information can be included in apayload of a link layer packet. In this case, the transmitter can embedidentification information for identifying the type of the headercompression signaling information, which is included in the payload ofthe link layer packet, in the header of the link layer packet or atransmission parameter (signaling information of the physical layer) ofthe physical layer and transmit the link layer packet header or thetransmission parameter including the identification information to thereceiver.

According to an embodiment, the identification information can indicatethat initialization information is included in the payload of the linklayer packet when the value thereof is 000 and indicate that aconfiguration parameter is included in the payload of the link layerpacket when the value thereof is 001. In addition, the identificationinformation can indicate that static chain information is included inthe payload of the link layer packet when the value thereof is 010 andindicate that dynamic chain information is included in the payload ofthe link layer packet when the value thereof is 011.

Here, the header compression signaling information may be called contextinformation. According to an embodiment, the static chain information orthe dynamic chain information may be called context information or boththe static chain information and the dynamic chain information may becalled context information.

FIG. 53 illustrates initialization information according to anembodiment of the present invention.

Initialization information included in a payload of a link layer packetmay include num_RoHC_channel information, max_cid information,large_cids information, num_profiles information, profile( ) element,num_IP_stream information and/or IP_address ( ) element.

The num_RoHC_channel information indicates the number of RoHC channels.

The max_cid information is used to indicate a maximum CID value to adecompressor.

The large_cid information has a Boolean value and indicates whether ashort CID (0˜15) or embedded CID (0˜16383) is used for a CIDconfiguration. Accordingly, bytes representing a CID are determined.

The num_profiles information indicates the number of RoHC profiles.

The profile( ) element includes information about a header compressionprotocol in RoHC. In RoHC, a stream can be compressed and recovered onlywhen the compressor and the decompressor have the same profile.

The num_IP_stream information indicates the number of IP streams.

The IP_address ( ) element includes the IP address of aheader-compressed IP packet.

FIG. 54 illustrates a configuration parameter according to an embodimentof the present invention.

A configuration parameter included in a link layer packet payload mayinclude RoHC_channel_id information, num_context information, context_idinformation, context_profile information, packet_configuration_modeinformation and/or context transmission mode information.

The RoHC_channel_id information identifies an RoHC channel.

The num_context information indicates the number of RoHC contexts.

The context_id information identifies an RoHC context. The context_idinformation can indicate a context to which the following RoHC relatedfield corresponds. The context_id information can correspond to acontext identifier (CID).

The context_profile information includes information about a headercompression protocol in RoHC. In RoHC, a stream can be compressed andrecovered only when the compressor and the decompressor have the sameprofile.

The packet_configuration_mode information identifies a packetconfiguration mode. Packet configuration modes have been describedabove.

The context_transmission_mode information identifies a contexttransmission mode. Context transmission modes have been described above.A context can be transmitted through a path through which normalbroadcast data is delivered or a path allocated for signalinginformation transmission.

FIG. 55 illustrates static chain information according to an embodimentof the present invention.

Static chain information included in a link layer packet payload mayinclude context_id information, context_profile information,static_chain_length information, static_chain ( ) element,dynamic_chain_incl information, dynamic_chain_length information and/ora dynamic_chain ( ) element.

The context_id information identifies an RoHC context. The context_idinformation can indicate a context to which the following RoHC relatedfield corresponds. The context_id information can correspond to acontext identifier (CID).

The context_profile information includes information about a headercompression protocol in RoHC. In RoHC, a stream can be compressed andrecovered only when the compressor and the decompressor have the sameprofile.

The static_chain_length information indicates the length of thestatic_chain ( ) element.

The static_chain ( ) element includes information belonging to a staticchain extracted from an upper layer packet during RoHC headercompression.

The dynamic_chain_incl information indicates whether dynamic chaininformation is included.

The dynamic_chain_length information indicates the length of thedynamic_chain ( ) element.

The dynamic_chain ( ) element includes information belonging to adynamic chain extracted from the upper layer packet during RoHC headercompression.

FIG. 56 illustrates dynamic chain information according to an embodimentof the present invention.

Dynamic chain information included in a link layer packet payload mayinclude context_id information, context_profile information,dynamic_chain_length information and/or a dynamic_chain ( ) element.

The context_id information identifies an RoHC context. The context_idinformation can indicate a context to which the following RoHC relatedfield corresponds. The context_id information can correspond to acontext identifier (CID).

The context_profile information includes information about a headercompression protocol in RoHC. In RoHC, a stream can be compressed andrecovered only when the compressor and the decompressor have the sameprofile.

The dynamic_chain_length information indicates the length of thedynamic_chain ( ) element.

The dynamic_chain ( ) element includes information belonging to adynamic chain extracted from an upper layer packet during RoHC headercompression.

FIG. 57 is a diagram illustrating a header structure of a link layerpacket when an MPEG-2 transport stream (TS) is input to a link layer,according to an embodiment of the present invention.

A packet type element may identify that an MPEG-2 TS packet is input toa link layer. For example, in this case, a value of the packet typeelement may be 011B.

The diagram illustrates a header structure of a link layer packet whenthe MPEG-2 TS is input. When the MPEG-2 TS packet is input to the linklayer, a header of the link layer packet may include a packet typeelement, a count field, a PID indicator (PI) field, and/or a deletednull packet indicator (DI) field.

For example, a count field of 2 bits or 3 bits, a PID indicator (PI)field of 1 bit, and a deleted null packet indicator (DI) of 1 bit may besubsequent to a packet type element of a header of a link layer packet.When 2 bits are used as a count field, the remaining 1 bit may bereserved as a reserved field for other future use. According toapposition of the reserved field, a fixed header part may be configuredwith various structures as illustrated in FIGS. 16(a) to 16(d). Althoughthe present invention is described in terms of a header illustrated inFIG. 57(a), the same description may also be applied to other types ofheaders.

When a MPEG-2 TS packet is input to a link layer, an extended header maynot be used in packet type=011.

A count field may identify the number of MPEG-2 TS packets contained ina payload of a link layer packet. A size of one MPEG-2 TS packet is verysmall compared with an input size of low-density parity-check (LDPC) asan FEC scheme that is likely to be employed in a physical layer of anext-generation broadcasting system, and thus concatenation of MPEG-2 TSpackets in a link layer may be basically considered. That is, one ormore MPEG-2 TS packets may be contained in a payload of a link layerpacket. However, the number of concatenated MPEG-2 TS packets may belimited to be identified as 2 bits or 3 bits. A length of a MPEG-2 TSpacket has a predetermined size (e.g., 188 bytes), and thus a receivercan also infer a size of a payload of a link layer packet using a countfield. An example for determining the number of MPEG-2 TS packetsaccording to a count field value will be described later.

A common PID indicator (PI) field may be set to 1 when packetidentifiers (PIDs) of MPEG-2 TS packets contained in a payload of onelink layer packet are the same, and otherwise, the common PI field maybe set to 0. The common PI field may have a 1 bit size.

A null packet deletion indicator (DI) field may be set to 1 when a nullpacket contained and transmitted in a MPEG-2 TS packet is deleted, andotherwise, the null packet DI may be set to 0. The null packet DI fieldmay have a size of 1 bit. When a DI field is 1, the receiver may reusesome fields of the MPEG-2 TS packet in order to support null packetdeletion in a link layer.

FIG. 58 is a diagram illustrating the number of MPEG-2 TS packetsincluded in a payload of a link layer packet according to a value of acount field, according to an embodiment of the present invention.

When the count field is 2 bits, there may be 4 numbers of cases withrespect to the number of concatenated MPEG-2 TS packets. The size of thepayload of the link layer packet except for a sync byte (47H) may alsobe identified by the count field.

The number of MPEG-2 TS packets allocated according to the number ofcount fields may be changed according to a system designer.

FIG. 59 is a diagram illustrating a header of an MPEG-2 TS packetaccording to an embodiment of the present invention.

The header of the MPEG-2 TS packet may include a sync byte field, atransport error indicator field, a payload unit start indicator field, atransport priority field, a PID field, a transport scrambling controlfield, an adaptation field control field, and/or a continuity counterfield.

The sync byte field may be used for packet synchronization and excludedduring encapsulation in a link layer. A transport error indicator (EI)positioned immediately after the sync byte field may not be used by atransmitter, and when an unrestorable error occurs in the receiver, thetransport EI may be used to indicate the error to a higher layer. Due tothis purpose, the transport EI field may be a bit that is not used bythe transmitter.

When error cannot be corrected in a stream, the transport EI field maybe field that is set during a demodulation process and indicates thatthere is error that cannot be corrected in a packet.

The payload unit start indicator field may identify whether a packetizedelementary stream (PES) or program-specific information (PSI) isstarted.

The transport priority field may identify whether a packet has higherpriority than other packets having the same PID.

The PID field may identify a packet.

The transport scrambling control field may identify whether a scrambleis used and/or whether a scramble is used using an odd numbered key oran even numbered key.

The adaptation field control field may identify whether an adaptationfield is present.

The continuity counter field may indicate a sequence number of a payloadpacket.

FIG. 60 is a diagram illustrating a procedure for changing use of atransport EI field by a transmitter according to an embodiment of thepresent invention.

As illustrated, when a DI field is 1, a transport error indicator fieldmay be changed to use of a deletion point indicator (DPI) field in alink layer of the transmitter. The DPI field may be restored to thetransport error indicator field after a null packet related processingis completed in the link layer of the receiver. That is, the DI fieldmay be a field that simultaneously indicates whether use of thetransport error indicator field is changed as well as whether a nullpacket is deleted.

FIG. 61 is a diagram illustrating a procedure for encapsulating anMPEG-2 TS packet according to an embodiment of the present invention.

Basically, the MPEG-2 TS packet is concatenated, and thus a payload ofone link layer packet may include a plurality of MPEG-2 TS packets, andthe number of the MPEG-2 TS packets may be determined according to theaforementioned method. When the number of MPEG-2 TS packets included ina payload of one link layer packet is n, each MPEG-2 TS packet may berepresented by Mk (1≤k≤n).

The MPEG-2 TS packet may include a fixed header of 4 bytes and a payloadof 184 bytes in general. 1 byte of a header of 4 bytes may be the syncbyte that has the same value 47H. Accordingly, one MPEG-2 TS packet ‘Mk’may include a sync part S of 1 byte, a fixed header part Hk of 3 bytesexcept for sync byte, and/or a payload part Pk of 184 bytes (here,1≤k≤n).

When the adaptation field is used in a header of the MPEG-2 TS packet,the fixed header part may be included in a portion immediately in frontof the adaptation field and the payload part may be included in theremaining adaptation part.

When n input MPEG-2 TS packets are [M1, M2, M3, . . . , Mn], the inputMPEG-2 TS packets may have arrangement of [S, H1, P1, S, H2, P2, . . . ,S, Hn, Pn]. The sync part may always have the same value, and in thisregard, even if the transmitter does not transmit the sync part, thereceiver may find a corresponding position in the receiver and re-insertthe sync part into the corresponding position. Accordingly, when apayload of a link layer packet is configured, the synch part may beexcluded to reduce the size of a packet. When a combination of an MPEG-2TS packet having the arrangement is configured with a payload of a linklayer packet, a header part and a payload part may be segmented with[H1, H2, . . . , Hn, P1, P2, . . . , Pn].

When a PI field value is 0, and a DI field value is 0, a length of apayload of a link layer packet is (n×3)+(n×184) bytes, and when 1 byteof a header length of the link layer packet is added, a total link layerpacket length may be obtained. That is, the receiver may identify alength of a link layer packet through this procedure.

FIG. 62 is a diagram illustrating a procedure for encapsulating MPEG-2TS packets having the same PIDs, according to an embodiment of thepresent invention.

When broadcasting data is continuously streamed, PID values of MPEG-2TSs included in one link layer packet may be the same. In this case,repeated PID values may be simultaneously marked so as to reduce a sizeof a link layer packet. In this case, a PID indicator (PI) field in aheader of a link layer packet may be used.

A common PID indicator (PI) value of the header of the link layer packetmay be set to 1. As described above, in the payload of the link layerpacket, n input MPEG-2 TS packets [M1, M2, M3, . . . , Mn] may bearranged in [H1, H2, . . . , Hn, P1, P2, . . . , Pn] by excluding thesync part and segmenting a header part and a payload part. Here, thecase in which a header part [H1, H2, . . . , Hn] of the MPEG-2 TS hasthe same PID, and thus even if a PID is marked only once, the receivermay restore the PID to an original header. When a common PID is a commonPID (CPID) and a header obtained by excluding PID from a header Hk ofthe MPEG-2 TS packet is H′k (1≤k≤n), a header part [H1, H2, . . . , Hn]of the MPEG-2 TS included in a payload of a link layer packet isreconfigured as [CPID, H′1, H′2, H′n]. This procedure may be referred toas common PID reduction.

FIG. 63 is a diagram illustrating an equation for obtaining a length ofa link layer packet during a common PID reduction procedure and a commonPID reduction procedure, according to an embodiment of the presentinvention.

A header part of a MPEG-2 TS packet may include a PID with a size of 13bits. When MPEG-2 TS packets included in a payload of a link layerpacket have the same PID value, PIDs may be repeated by as much as thenumber of concatenated packets. Accordingly, a PID part may be excludedfrom a header part [H1, H2, . . . , Hn] of an original MPEG-2 TS packetto reconfigure [H′1, H′2, . . . , H′n], a value of the common PID may beset to a value of a common PID (CPID), and then the CIPD may bepositioned in front of the reconfigured header part.

The PID value may have a length of 13 bits, and a stuffing bit may beadded in order to form all packets in the form of a byte unit. Thestuffing bit may be positioned in front of or behind the CPID and may beappropriately arranged according to a configuration of otherconcatenated protocol layers or embodiments of a system.

In the case of encapsulation of MPEG-2 TS packets having the same PID,the PID may be excluded from the header part of the MPEG-2 TS packet andan encapsulation procedure is performed, and thus the length of apayload of a link layer packet may be obtained as follows.

As illustrated, a header of a MPEG-2 TS packet obtained by excluding thesync byte may have a length of 3 bytes, and when a PID part of 13 bitsmay be excluded from the header of the MPEG-2 TS packet, the header ofthe MPEG-2 TS packet may be 11 bits. Accordingly, when n packets areconcatenated, the packets have (n×11) bits, and when the number ofconcatenated packets is set to a multiple of 8, (n×11) bits may be alength of a byte unit. Here, a stuffing bit with a length of 3 bits maybe added to 13 bits as a common PID length to configure a CPID part witha length of 2 bytes.

Accordingly, in the case of a link layer packet formed by encapsulatingn MPEG-2 TS packets having the same PID, when a header length of a linklayer packet is LH, a length of a CPID part is LCPID, and a total lengthof a link layer packet is LT, LT may be obtained according to the shownequation.

In the embodiment illustrated in FIG. 62, LH may be 1 byte and LCPID maybe 2 bytes.

FIG. 64 is a diagram illustrating the number of concatenated MPEG-2 TSpackets according to a value of a count field and a length of a linklayer packet according to the number when common PID reduction isapplied, according to an embodiment of the present invention.

When the number of the concatenated MPEG-2 TS packets are determined, ifall packets have the same PID, the aforementioned common PID reductionprocedure may be applied, and the receiver may acquire a length of alink layer packet according to the equation described in relation to theprocedure.

FIG. 65 is a diagram illustrating a method for encapsulating an MPEG-2TS packet including a null packet, according to an embodiment of thepresent invention.

During transmission of the MPEG-2 TS packet, the null packet may beincluded in a transport stream for adjustment to a fixed transfer rate.The null packet is an overhead part in terms of transmission, and thuseven if a transmitter does not transmit the null packet, a receiver mayrestore the null packet. In order to delete and transmit the null packetby the transmitter and find and restore the number and position of thedeleted packets by the receiver, a null packet deletion indicator (DI)field in the header of the link layer packet may be used. In this case,a value of the null packet deletion indictor (DI) of the header of thelink layer packet may be set to 1.

Encapsulation when a null packet is positioned at an arbitrary pointbetween input transport streams may be performed by sequentiallyconcatenating n packets except for the null packet. The number ofcounted null packets that are continuously excluded may be contained ina payload of a link layer packet, and the receiver may generate and filla null packet in an original position based on the count value.

When n MPEG-2 TS packets except for the null packet is [M1, M2, M3, . .. , Mn], the null packet may be positioned at any position between M1 toMn. One link layer packet may include a counted number of null packetswith a number of times of 0 to n. That is, when a number of times thatnull packets are counted in one link layer packet is p, a range of p maybe 0 to n.

When a count value of null packets is Cm, a range of m may be 1≤m≤p, andwhen p=0, Cm is not present. As described above, MPEG-2 TS packetsbetween which Cm is positioned may be indicated using a field in aheader of the MPEG-2 TS packet, in which use of a transport errorindicator (EI) is changed to a deletion point indicator (DPI).

The present invention proposes a case in which Cm has a length of 1 byteand also considers a case in which Cm is extended when there is a marginfor a length of a packet for future use. Cm of 1-byte length may count amaximum of 256 null packets. A field that functions as an indicator of anull packet is positioned in a header of a MPEG-2 TS packet, and thuscalculation may be performed by excluding null packets by as much as avalue obtained by adding 1 to a value indicated by Cm. For example, inthe case of Cm=0, one null packet may be excluded, and in the case ofCm=123, 124 null packets may be excluded. When continuous null packetsexceed 256, a 257th null packet may be processed as a normal packet, andnext null packets may be processed as null packets using theaforementioned method.

As illustrated, when null packets may be positioned between MPEG-2 TSpackets corresponding to Mi and Mi+1, a counted number of the nullpackets is C1, and when a null packet is positioned between MPEG-2 TSpackets corresponding to Mj and Mj+1, a counted number of the nullpackets is Cp, and in this case, an actual transmission sequence may be[ . . . , Mi, C1, Mi+1, Mj, Cp, Mj+1, . . . ].

In a procedure for segmenting and reordering a header part and a payloadpart of an MPEG-2 TS packet instead of a null packet in order toconfigure a payload of a link layer packet, a count value Cm (1≤m≤p) ofnull packets may be disposed between the header part and the payload ofthe MPEG-2 TS packet. That is, the payload of the link layer packet maybe disposed like [H1, H2, Hn, C1, . . . , Cp, P1, P2, . . . , Pn], and areceiver may sequentially check a count value on a byte-by-byte basis atan order indicated in a DPI field of Hk and restore a null packet at anoriginal order of an MPEG-2 TS packet by as much as the count value.

FIG. 66 is a diagram illustrating a procedure for processing anindicator for counting deleted null packets and an equation forobtaining a length of a link layer packet during the procedure,according to an embodiment of the present invention.

A value of a DPI field may be set to indicate that null packets aredeleted and a count value of the deleted null packets is present. Asillustrated, when a value of a DPI field in Hi of a header of aplurality of MPEG-2 TS packets is 1, this may indicate that the MPEG-2TS packets are encapsulated by excluding an null packet between Hi andHi+1 and 1-byte count value according thereto is positioned between aheader part and a payload part.

During this procedure, a length of a link layer packet may be calculatedaccording to the shown equation. Accordingly, in the case of a linklayer packet obtained by encapsulating n MPEG-2 TS packets from which anull packet is excluded, when a header length of the link layer packetis LH, a length of a count value Cm (1≤m≤p) of a null packet is LCount,and a total length of the link layer packet is LT, LT may be acquiredaccording to the shown equation.

FIG. 67 is a diagram illustrating a procedure for encapsulating anMPEG-2 TS packet including a null packet, according to anotherembodiment of the present invention.

Another encapsulation method for excluding a null packet, a payload of alink layer packet may be configured. According to another embodiment ofthe present invention, in a procedure for segmenting and reordering aheader part and a payload part of a MPEG-2 TS packet in order toconfigure a payload of a link layer packet, a count value Cm (1≤m≤p) ofnull packets may be positioned in a header part and an order of the nullpackets may be maintained. That is, a header of each MPEG-2 TS mayinclude a count value of null packets at a point in which a header ends.Accordingly, upon reading a value of a DPI field contained in a headerof each MPEG-2 TS and determining that the null packets are deleted, thereceiver may read a count value contained in a last part of thecorresponding header, regenerate null packets by as much as thecorresponding count value, and contain the null packets in a stream.

FIG. 68 is a diagram illustrating a procedure for encapsulating MPEG-2TS packets including the same packet identifier (PID) in a streamincluding a null packet, according to an embodiment of the presentinvention.

According to an embodiment of the present invention, in a streamincluding null packets, a procedure for encapsulating MPEG-2 TS packetsincluding the same packet identifier (PID) may be performed by combininga procedure for encapsulating a link layer packet by excluding theaforementioned null packet and a procedure for encapsulating MPEG-2 TSpackets having the same PID as a link layer packet.

Since null packets are allocated separate PIDs indicating the respectivenull packet, when the null packet are contained in an actual transportstream, the null packets are not processed with the same PID. However,after a procedure for excluding a null packet is performed, since only acount value of null packets is contained in a payload of a link layerpacket, the remaining n MPEG-2 TS packets have the same PID, and thusthe null packets may be processed using the aforementioned method.

FIG. 69 is a diagram illustrating an equation for obtaining a length ofa link layer packet while MPEG-2 TS packets including the same packetidentifier (PID) are encapsulated in a stream including a null packet,according to an embodiment of the present invention.

While MPEG-2 TS packets including the same packet identifier (PID) areencapsulated in a stream including null packets, a length of a linklayer packet may be derived according to the equation of FIGS. 63 and/or66. This may be summarized to obtain the illustrated equation.

FIG. 70 is a view showing a protocol stack for a next generationbroadcasting system according to an embodiment of the present invention.

The broadcasting system according to the present invention maycorrespond to a hybrid broadcasting system in which an Internet Protocol(IP) centric broadcast network and a broadband are coupled.

The broadcasting system according to the present invention may bedesigned to maintain compatibility with a conventional MPEG-2 basedbroadcasting system.

The broadcasting system according to the present invention maycorrespond to a hybrid broadcasting system based on coupling of an IPcentric broadcast network, a broadband network, and/or a mobilecommunication network (or a cellular network).

Referring to the figure, a physical layer may use a physical protocoladopted in a broadcasting system, such as an ATSC system and/or a DVBsystem. For example, in the physical layer according to the presentinvention, a transmitter/receiver may transmit/receive a terrestrialbroadcast signal and convert a transport frame including broadcast datainto an appropriate form.

In an encapsulation layer, an IP datagram is acquired from informationacquired from the physical layer or the acquired IP datagram isconverted into a specific frame (for example, an RS Frame, GSE-lite,GSE, or a signal frame). The frame main include a set of IP datagrams.For example, in the encapsulation layer, the transmitter include dataprocessed from the physical layer in a transport frame or the receiverextracts an MPEG-2 TS and an IP datagram from the transport frameacquired from the physical layer.

A fast information channel (FIC) includes information (for example,mapping information between a service ID and a frame) necessary toaccess a service and/or content. The FIC may be named a fast accesschannel (FAC).

The broadcasting system according to the present invention may useprotocols, such as an Internet Protocol (IP), a User Datagram Protocol(UDP), a Transmission Control Protocol (TCP), an Asynchronous LayeredCoding/Layered Coding Transport (ALC/LCT), a Rate Control Protocol/RTPControl Protocol (RCP/RTCP), a Hypertext Transfer Protocol (HTTP), and aFile Delivery over Unidirectional Transport (FLUTE). A stack betweenthese protocols may refer to the structure shown in the figure.

In the broadcasting system according to the present invention, data maybe transported in the form of an ISO based media file format (ISOBMFF).An Electrical Service Guide (ESG), Non Real Time (NRT), Audio/Video(A/V), and/or general data may be transported in the form of theISOBMFF.

Transport of data through a broadcast network may include transport of alinear content and/or transport of a non-linear content.

Transport of RTP/RTCP based A/V and data (closed caption, emergencyalert message, etc.) may correspond to transport of a linear content.

An RTP payload may be transported in the form of an RTP/AV streamincluding a Network Abstraction Layer (NAL) and/or in a formencapsulated in an ISO based media file format. Transport of the RTPpayload may correspond to transport of a linear content. Transport inthe form encapsulated in the ISO based media file format may include anMPEG DASH media segment for A/V, etc.

Transport of a FLUTE based ESG, transport of non-timed data, transportof an NRT content may correspond to transport of a non-linear content.These may be transported in an MIME type file form and/or a formencapsulated in an ISO based media file format. Transport in the formencapsulated in the ISO based media file format may include an MPEG DASHmedia segment for A/V, etc.

Transport through a broadband network may be divided into transport of acontent and transport of signaling data.

Transport of the content includes transport of a linear content (AN anddata (closed caption, emergency alert message, etc.)), transport of anon-linear content (ESG, non-timed data, etc.), and transport of a MPEGDASH based Media segment (A/V and data).

Transport of the signaling data may be transport including a signalingtable (including an MPD of MPEG DASH) transported through a broadcastingnetwork.

In the broadcasting system according to the present invention,synchronization between linear/non-linear contents transported throughthe broadcasting network or synchronization between a contenttransported through the broadcasting network and a content transportedthrough the broadband may be supported. For example, in a case in whichone UD content is separately and simultaneously transported through thebroadcasting network and the broadband, the receiver may adjust thetimeline dependent upon a transport protocol and synchronize the contentthrough the broadcasting network and the content through the broadbandto reconfigure the contents as one UD content.

An applications layer of the broadcasting system according to thepresent invention may realize technical characteristics, such asInteractivity, Personalization, Second Screen, and automatic contentrecognition (ACR). These characteristics are important in extension fromATSC 2.0 to ATSC 3.0. For example, HTML5 may be used for acharacteristic of interactivity.

In a presentation layer of the broadcasting system according to thepresent invention, HTML and/or HTML5 may be used to identify spatial andtemporal relationships between components or interactive applications.

In the present invention, signaling includes signaling informationnecessary to support effective acquisition of a content and/or aservice. Signaling data may be expressed in a binary or XMK form. Thesignaling data may be transmitted through the terrestrial broadcastingnetwork or the broadband.

A real-time broadcast A/V content and/or data may be expressed in an ISOBase Media File Format, etc. In this case, the A/V content and/or datamay be transmitted through the terrestrial broadcasting network in realtime and may be transmitted based on IP/UDP/FLUTE in non-real time.Alternatively, the broadcast A/V content and/or data may be received byreceiving or requesting a content in a streaming mode using DynamicAdaptive Streaming over HTTP (DASH) through the Internet in real time.In the broadcasting system according to the embodiment of the presentinvention, the received broadcast A/V content and/or data may becombined to provide various enhanced services, such as an Interactiveservice and a second screen service, to a viewer.

In a hybrid-based broadcast system of a TS and an IP stream, a linklayer may be used to transmit data having a TS or IP stream type. Whenvarious types of data are to be transmitted through a physical layer,the link layer may convert the data into a format supported by thephysical layer and deliver the converted data to the physical layer. Inthis way, the various types of data may be transmitted through the samephysical layer. Here, the physical layer may correspond to a step oftransmitting data using an MIMO/MISO scheme or the like by interleaving,multiplexing, and/or modulating the data.

The link layer needs to be designed such that an influence on anoperation of the link layer is minimized even when a configuration ofthe physical layer is changed. In other words, the operation of the linklayer needs to be configured such that the operation may be compatiblewith various physical layers.

The present invention proposes a link layer capable of independentlyoperating irrespective of types of an upper layer and a lower layer. Inthis way, it is possible to support various upper layers and lowerlayers. Here, the upper layer may refer to a layer of a data stream suchas a TS stream, an IP stream, or the like. Here, the lower layer mayrefer to the physical layer. In addition, the present invention proposesa link layer having a correctable structure in which a functionsupportable by the link layer may be extended/added/deleted. Moreover,the present invention proposes a scheme of including an overheadreduction function in the link layer such that radio resources may beefficiently used.

In this figure, protocols and layers such as IP, UDP, TCP, ALC/LCT,RCP/RTCP, HTTP, FLUTE, and the like are as described above.

In this figure, a link layer t88010 may be another example of theabove-described data link (encapsulation) part. The present inventionproposes a configuration and/or an operation of the link layer t88010.The link layer t88010 proposed by the present invention may processsignaling necessary for operations of the link layer and/or the physicallayer. In addition, the link layer t88010 proposed by the presentinvention may encapsulate TS and IP packets and the like, and performoverhead reduction in this process.

The link layer t88010 proposed by the present invention may be referredto by several terms such as data link layer, encapsulation layer, layer2, and the like. According to a given embodiment, a new term may beapplied to the link layer and used.

FIG. 71 is a conceptual diagram illustrating an interface of a linklayer according to an embodiment of the present invention.

Referring to FIG. 71, the transmitter may consider an exemplary case inwhich IP packets and/or MPEG-2 TS packets mainly used in the digitalbroadcasting are used as input signals. The transmitter may also supporta packet structure of a new protocol capable of being used in the nextgeneration broadcast system. The encapsulated data of the link layer andsignaling information may be transmitted to a physical layer. Thetransmitter may process the transmitted data (including signaling data)according to the protocol of a physical layer supported by the broadcastsystem, such that the transmitter may transmit a signal including thecorresponding data.

On the other hand, the receiver may recover data and signalinginformation received from the physical layer into other data capable ofbeing processed in a upper layer. The receiver may read a header of thepacket, and may determine whether a packet received from the physicallayer indicates signaling information (or signaling data) or recognitiondata (or content data).

The signaling information (i.e., signaling data) received from the linklayer of the transmitter may include first signaling information that isreceived from an upper layer and needs to be transmitted to an upperlayer of the receiver; second signaling information that is generatedfrom the link layer and provides information regarding data processingin the link layer of the receiver; and/or third signaling informationthat is generated from the upper layer or the link layer and istransferred to quickly detect specific data (e.g., service, content,and/or signaling data) in a physical layer.

FIG. 72 illustrates an operation in a normal mode corresponding to oneof operation modes of a link layer according to an embodiment of thepresent invention.

The link layer proposed by the present invention may have variousoperation modes for compatibility between an upper layer and a lowerlayer. The present invention proposes a normal mode and a transparentmode of the link layer. Both the operation modes may coexist in the linklayer, and an operation mode to be used may be designated usingsignaling or a system parameter. According to a given embodiment, one ofthe two operation modes may be implemented. Different modes may beapplied according to an IP layer, a TS layer, and the like input to thelink layer. In addition, different modes may be applied for each streamof the IP layer and for each stream of the TS layer.

According to a given embodiment, a new operation mode may be added tothe link layer. The new operation mode may be added based onconfigurations of the upper layer and the lower layer. The new operationmode may include different interfaces based on the configurations of theupper layer and the lower layer. Whether to use the new operation modemay be designated using signaling or a system parameter.

In the normal mode, data may be processed through all functionssupported by the link layer, and then delivered to a physical layer.

First, each packet may be delivered to the link layer from an IP layer,an MPEG-2 TS layer, or another particular layer t89010. In other words,an IP packet may be delivered to the link layer from an IP layer.Similarly, an MPEG-2 TS packet may be delivered to the link layer fromthe MPEG-2 TS layer, and a particular packet may be delivered to thelink layer from a particular protocol layer.

Each of the delivered packets may go through or not go through anoverhead reduction process t89020, and then go through an encapsulationprocess t89030.

First, the IP packet may go through or not go through the overheadreduction process t89020, and then go through the encapsulation processt89030. Whether the overhead reduction process t89020 is performed maybe designated by signaling or a system parameter. According to a givenembodiment, the overhead reduction process t89020 may be performed ornot performed for each IP stream. An encapsulated IP packet may bedelivered to the physical layer.

Second, the MPEG-2 TS packet may go through the overhead reductionprocess t89020, and go through the encapsulation process t89030. TheMPEG-2 TS packet may not be subjected to the overhead reduction processt89020 according to a given embodiment. However, in general, a TS packethas sync bytes (0x47) and the like at the front and thus it may beefficient to eliminate such fixed overhead. The encapsulated TS packetmay be delivered to the physical layer.

Third, a packet other than the IP or TS packet may or may not go throughthe overhead reduction process t89020, and then go through theencapsulation process t89030. Whether or not the overhead reductionprocess t89020 is performed may be determined according tocharacteristics of the corresponding packet. Whether the overheadreduction process t89020 is performed may be designated by signaling ora system parameter. The encapsulated packet may be delivered to thephysical layer.

In the overhead reduction process t89020, a size of an input packet maybe reduced through an appropriate scheme. In the overhead reductionprocess t89020, particular information may be extracted from the inputpacket or generated. The particular information is information relatedto signaling, and may be transmitted through a signaling region. Thesignaling information enables a receiver to restore an original packetby restoring changes due to the overhead reduction process t89020. Thesignaling information may be delivered to a link layer signaling processt89050.

The link layer signaling process t89050 may transmit and manage thesignaling information extracted/generated in the overhead reductionprocess t89020. The physical layer may have physically/logically dividedtransmission paths for signaling, and the link layer signaling processt89050 may deliver the signaling information to the physical layeraccording to the divided transmission paths. Here, the above-describedFIC signaling process t89060, EAS signaling process t89070, or the likemay be included in the divided transmission paths. Signaling informationnot transmitted through the divided transmission paths may be deliveredto the physical layer through the encapsulation process t89030.

Signaling information managed by the link layer signaling process t89050may include signaling information delivered from the upper layer,signaling information generated in the link layer, a system parameter,and the like. Specifically, the signaling information may includesignaling information delivered from the upper layer to be subsequentlydelivered to an upper layer of the receiver, signaling informationgenerated in the link layer to be used for an operation of a link layerof the receiver, signaling information generated in the upper layer orthe link layer to be used for rapid detection in a physical layer of thereceiver, and the like.

Data going through the encapsulation process t89030 and delivered to thephysical layer may be transmitted through a data pipe (DP) t89040. Here,the DP may be a physical layer pipe (PLP). Signaling informationdelivered through the above-described divided transmission paths may bedelivered through respective transmission paths. For example, an FICsignal may be transmitted through an FIC t89080 designated in a physicalframe. In addition, an EAS signal may be transmitted through an EACt89090 designated in a physical frame. Information about presence of adedicated channel such as the FIC, the EAC, or the like may betransmitted to a preamble area of the physical layer through signaling,or signaled by scrambling a preamble using a particular scramblingsequence. According to a given embodiment, FIC signaling/EAS signalinginformation may be transmitted through a general DP area, PLS area, orpreamble rather than a designated dedicated channel.

The receiver may receive data and signaling information through thephysical layer. The receiver may restore the received data and signalinginformation into a form processable in the upper layer, and deliver therestored data and signaling information to the upper layer. This processmay be performed in the link layer of the receiver. The receiver mayverify whether a received packet is related to the signaling informationor the data by reading a header of the packet and the like. In addition,when overhead reduction is performed at a transmitter, the receiver mayrestore a packet, overhead of which has been reduced through theoverhead reduction process, to an original packet. In this process, thereceived signaling information may be used.

FIG. 73 illustrates an operation in a transparent mode corresponding toone of operation modes of a link layer according to an embodiment of thepresent invention.

In the transparent mode, data may not be subjected to functionssupported by the link layer or may be subjected to some of thefunctions, and then delivered to a physical layer. In other words, inthe transparent mode, a packet delivered to an upper layer may bedelivered to a physical layer without going through a separate overheadreduction and/or encapsulation process. Other packets may go through theoverhead reduction and/or encapsulation process as necessary. Thetransparent mode may be referred to as a bypass mode, and another termmay be applied to the transparent mode.

According to a given embodiment, some packets may be processed in thenormal mode and some packets may be processed in the transparent modebased on characteristics of the packets and a system operation.

A packet to which the transparent mode may be applied may be a packethaving a type well known to a system. When the packet may be processedin the physical layer, the transparent mode may be used. For example, awell-known TS or IP packet may go through separate overhead reductionand input formatting processes in the physical layer and thus thetransparent mode may be used in a link layer step. When the transparentmode is applied and a packet is processed through input formatting andthe like in the physical layer, an operation such as the above-describedTS header compression may be performed in the physical layer. On theother hand, when the normal mode is applied, a processed link layerpacket may be treated as a GS packet and processed in the physicallayer.

In the transparent mode, a link layer signaling module may be includedwhen signal transmission needs to be supported. As described above, thelink layer signaling module may transmit and manage signalinginformation. The signaling information may be encapsulated andtransmitted through a DP, and FIC signaling information and EASsignaling information having divided transmission paths may betransmitted through an FIC and an EAC, respectively.

In the transparent mode, whether information corresponds to signalinginformation may be displayed using a fixed IP address and port number.In this case, the signaling information may be filtered to configure alink layer packet, and then transmitted through the physical layer.

FIG. 74 illustrates a configuration of a link layer at a transmitteraccording to an embodiment of the present invention (normal mode).

The present embodiment is an embodiment presuming that an IP packet isprocessed. The link layer at the transmitter may largely include a linklayer signaling part for processing signaling information, an overheadreduction part, and/or an encapsulation part from a functionalperspective. The link layer at the transmitter may further include ascheduler t91020 for a control of the entire operation of the link layerand scheduling, input and output parts of the link layer, and/or thelike.

First, upper layer signaling information and/or system parameter t91010may be delivered to the link layer. In addition, an IP stream includingIP packets may be delivered to the link layer from an IP layer t91110.

As described above, the scheduler t91020 may determine and controloperations of several modules included in the link layer. The deliveredsignaling information and/or system parameter t91010 may be filtered orused by the scheduler t91020. Information corresponding to a part of thedelivered signaling information and/or system parameter t91010 andnecessary for a receiver may be delivered to the link layer signalingpart. In addition, information corresponding to a part of the signalinginformation and necessary for an operation of the link layer may bedelivered to an overhead reduction control block t91120 or anencapsulation control block t91180.

The link layer signaling part may collect information to be transmittedas signaling in the physical layer, and transform/configure theinformation in a form suitable for transmission. The link layersignaling part may include a signaling manager t91030, a signalingformatter t91040, and/or a buffer for channels t91050.

The signaling manager t91030 may receive signaling information deliveredfrom the scheduler t91020, signaling delivered from the overheadreduction part, and/or context information. The signaling manager t91030may determine paths for transmission of the signaling information withrespect to delivered data. The signaling information may be deliveredthrough the paths determined by the signaling manager t91030. Asdescribed in the foregoing, signaling information to be transmittedthrough divided channels such as an FIC, an EAS, and the like may bedelivered to the signaling formatter t91040, and other signalinginformation may be delivered to an encapsulation buffer t91070.

The signaling formatter t91040 may format associated signalinginformation in forms suitable for respective divided channels so thatthe signaling information may be transmitted through separately dividedchannels. As described in the foregoing, the physical layer may includephysically/logically divided separate channels. The divided channels maybe used to transmit FIC signaling information or EAS-relatedinformation. The FIC or EAS-related information may be divided by thesignaling manager t91030 and input to the signaling formatter t91040.The signaling formatter t91040 may format information such that theinformation is suitable for respective separate channels. Besides theFIC and the EAS, when the physical layer is designed to transmitparticular signaling information through separately divided channels, asignaling formatter for the particular signaling information may beadded. Through this scheme, the link layer may be compatible withvarious physical layers.

The buffer for channels t91050 may deliver signaling informationdelivered from the signaling formatter t91040 to designated dedicatedchannels t91060. The number and content of the dedicated channels t91060may vary depending on an embodiment.

As described in the foregoing, the signaling manager t91030 may deliversignaling information which is not delivered to a dedicated channel tothe encapsulation buffer t91070. The encapsulation buffer t91070 mayfunction as a buffer that receives the signaling information notdelivered to the dedicated channel.

An encapsulation for signaling information t91080 may encapsulate thesignaling information not delivered to the dedicated channel. Atransmission buffer t91090 may function as a buffer that delivers theencapsulated signaling information to a DP for signaling informationt91100. Here, the DP for signaling information t91100 may refer to theabove-described PLS area.

The overhead reduction part may allow efficient transmission byeliminating overhead of packets delivered to the link layer. It ispossible to configure overhead reduction parts, the number of which isthe same as the number of IP streams input to the link layer.

An overhead reduction buffer t91130 may receive an IP packet deliveredfrom an upper layer. The delivered IP packet may be input to theoverhead reduction part through the overhead reduction buffer t91130.

An overhead reduction control block t91120 may determine whether toperform overhead reduction on a packet stream input to the overheadreduction buffer t91130. The overhead reduction control block t91120 maydetermine whether to perform overhead reduction for each packet stream.When overhead reduction is performed on the packet stream, packets maybe delivered to an RoHC compressor t91140 and overhead reduction may beperformed. When overhead reduction is not performed on the packetstream, packets may be delivered to the encapsulation part andencapsulation may be performed without overhead reduction. Whether toperform overhead reduction on packets may be determined by signalinginformation t91010 delivered to the link layer. The signalinginformation t91010 may be delivered to the encapsulation control blockt91180 by the scheduler t91020.

The RoHC compressor t91140 may perform overhead reduction on a packetstream. The RoHC compressor t91140 may compress headers of packets.Various schemes may be used for overhead reduction. Overhead reductionmay be performed by schemes proposed in the present invention. Thepresent embodiment presumes an IP stream and thus the compressor isexpressed as the RoHC compressor. However, the term may be changedaccording to a given embodiment. In addition, an operation is notrestricted to compression of an IP stream, and overhead reduction may beperformed on all types of packets by the RoHC compressor t91140.

A packet stream configuration block t91150 may divide IP packets havingcompressed headers into information to be transmitted to a signalingregion and information to be transmitted to a packet stream. Theinformation to be transmitted to the packet stream may refer toinformation to be transmitted to a DP area. The information to betransmitted to the signaling region may be delivered to a signalingand/or context control block t91160. The information to be transmittedto the packet stream may be transmitted to the encapsulation part.

The signaling and/or context control block t91160 may collect signalingand/or context information and deliver the collected information to thesignaling manager t91030. In this way, the signaling and/or contextinformation may be transmitted to the signaling region.

The encapsulation part may encapsulate packets in suitable forms suchthat the packets may be delivered to the physical layer. The number ofconfigured encapsulation parts may be the same as the number of IPstreams.

An encapsulation buffer t91170 may receive a packet stream forencapsulation. Packets subjected to overhead reduction may be receivedwhen overhead reduction is performed, and an input IP packet may bereceived without change when overhead reduction is not performed.

An encapsulation control block t91180 may determine whether to performencapsulation on an input packet stream. When encapsulation isperformed, the packet stream may be delivered tosegmentation/concatenation t91190. When encapsulation is not performed,the packet stream may be delivered to a transmission buffer t91230.Whether to perform encapsulation of packets may be determined based onthe signaling information t91010 delivered to the link layer. Thesignaling information t91010 may be delivered to the encapsulationcontrol block t91180 by the scheduler t91020.

In the segmentation/concatenation t91190, the above-descriedsegmentation or concatenation operation may be performed on packets. Inother words, when an input IP packet is longer than a link layer packetcorresponding to an output of the link layer, one IP packet may bedivided into several segments to configure a plurality of link layerpacket payloads. In addition, when the input IP packet is shorter thanthe link layer packet corresponding to the output of the link layer,several IP packets may be combined to configure one link layer packetpayload.

A packet configuration table t91200 may have information about aconfiguration of segmented and/or concatenated link layer packets. Atransmitter and a receiver may have the same information of the packetconfiguration table t91200. The transmitter and the receiver may referto the information of the packet configuration table t91200. An indexvalue of the information of the packet configuration table t91200 may beincluded in headers of the link layer packets.

A link layer header information block t91210 may collect headerinformation generated in an encapsulation process. In addition, the linklayer header information block t91210 may collect information includedin the packet configuration table t91200. The link layer headerinformation block t91210 may configure header information according to aheader configuration of a link layer packet.

A header attachment block t91220 may add headers to payloads of thesegmented and/or concatenated link layer packets. The transmissionbuffer t91230 may function as a buffer for delivering a link layerpacket to a DP t91240 of the physical layer.

Each block or module and parts may be configured as one module/protocolor a plurality of modules/protocols in the link layer.

FIG. 75 illustrates a configuration of a link layer at a receiveraccording to an embodiment of the present invention (normal mode).

The present embodiment is an embodiment presuming that an IP packet isprocessed. The link layer at the receiver may largely include a linklayer signaling part for processing signaling information, an overheadprocessing part, and/or a decapsulation part from a functionalperspective. The link layer at the receiver may further include ascheduler for a control of the entire operation of the link layer andscheduling, input and output parts of the link layer, and/or the like.

First, information received through a physical layer may be delivered tothe link layer. The link layer may process the information to restorethe information to an original state in which the information is not yetprocessed by a transmitter, and deliver the information to an upperlayer. In the present embodiment, the upper layer may be an IP layer.

Information delivered through dedicated channels t92030 separated fromthe physical layer may be delivered to the link layer signaling part.The link layer signaling part may distinguish signaling informationreceived from the physical layer, and deliver the distinguishedsignaling information to each part of the link layer.

A buffer for channels t92040 may function as a buffer that receivessignaling information transmitted through the dedicated channels. Asdescribed above, when physically/logically divided separate channels arepresent in the physical layer, it is possible to receive signalinginformation transmitted through the channels. When the informationreceived from the separate channels is in a divided state, the dividedinformation may be stored until the information is in a complete form.

A signaling decoder/parser t92050 may check a format of signalinginformation received through a dedicated channel, and extractinformation to be used in the link layer. When the signaling informationreceived through the dedicated channel is encoded, decoding may beperformed. In addition, according to a given embodiment, it is possibleto check integrity of the signaling information.

A signaling manager t92060 may integrate signaling information receivedthrough several paths. Signaling information received through a DP forsignaling t92070 to be described below may be integrated by thesignaling manager t92060. The signaling manager t92060 may deliversignaling information necessary for each part in the link layer. Forexample, context information for recovery of a packet and the like maybe delivered to the overhead processing part. In addition, signalinginformation for control may be delivered to a scheduler t92020.

General signaling information not received through a separate dedicatedchannel may be received through the DP for signaling t92070. Here, theDP for signaling may refer to a PLS or the like. A reception buffert92080 may function as a buffer for receiving the signaling informationreceived from the DP for signaling t92070. The received signalinginformation may be decapsulated in a decapsulation for signalinginformation block t92090. The decapsulated signaling information may bedelivered to the signaling manager t92060 through a decapsulation buffert92100. As described in the foregoing, the signaling manager t92060 maycollect signaling information and deliver the collected signalinginformation to a desired part in the link layer.

The scheduler t92020 may determine and control operations of severalmodules included in the link layer. The scheduler t92020 may controleach part of the link layer using receiver information t92010 and/orinformation delivered from the signaling manager t92060. In addition,the scheduler t92020 may determine an operation mode and the like ofeach part. Here, the receiver information t92010 may refer toinformation previously stored by the receiver. The scheduler t92020 mayuse information changed by a user such as a channel change and the likefor control.

The decapsulation part may filter a packet received from a DP t92110 ofthe physical layer, and separate the packet based on a type of thepacket. The number of configured decapsulation parts may be the same asthe number of DPs that may be simultaneously decoded in the physicallayer.

A decapsulation buffer t92120 may function as a buffer that receives apacket stream from the physical layer to perform decapsulation. Adecapsulation control block t92130 may determine whether to decapsulatethe received packet stream. When decapsulation is performed, the packetstream may be delivered to a link layer header parser t92140. Whendecapsulation is not performed, the packet stream may be delivered to anoutput buffer t92220, The signaling information delivered from thescheduler t92020 may be used to determine whether to performdecapsulation.

The link layer header parser t92140 may identify a header of a receivedlink layer packet. When the header is identified, it is possible toidentify a configuration of an IP packet included in a payload of thelink layer packet. For example, the IP packet may be segmented orconcatenated.

A packet configuration table t92150 may include payload information oflink layer packets configured through segmentation and/or concatenation.The transmitter and the receiver may have the same information asinformation of the packet configuration table t92150. The transmitterand the receiver may refer to the information of the packetconfiguration table t92150. A value necessary for reassembly may befound based on index information included in the link layer packets.

A reassembly block t92160 may configure payloads of the link layerpackets configured through segmentation and/or concatenation as packetsof an original IP stream. The reassembly block t92160 may reconfigureone IP packet by collecting segments, or reconfigure a plurality of IPpacket streams by separating concatenated packets. The reassembled IPpackets may be delivered to the overhead processing part.

The overhead processing part may perform a reverse process of overheadreduction performed by the transmitter. In the reverse process, anoperation of returning packets experiencing overhead reduction tooriginal packets is performed. This operation may be referred to asoverhead processing. The number of configured overhead processing partsmay be the same as the number of DPs that may be simultaneously decodedin the physical layer.

A packet recovery buffer t92170 may function as a buffer that receivesan RoHC packet or an IP packet decapsulated for overhead processing.

An overhead control block t92180 may determine whether to perform packetrecovery and/or decompression of decapsulated packets. When the packetrecovery and/or decompression are performed, the packets may bedelivered to a packet stream recovery t92190. When the packet recoveryand/or decompression are not performed, the packets may be delivered tothe output buffer t92220. Whether to perform the packet recovery and/ordecompression may be determined based on the signaling informationdelivered by the scheduler t92020.

The packet stream recovery t92190 may perform an operation ofintegrating a packet stream separated from the transmitter and contextinformation of the packet stream. The operation may correspond to aprocess of restoring the packet stream such that the packet stream maybe processed by an RoHC decompressor t92210. In this process, signalinginformation and/or context information may be delivered from a signalingand/or context control block t92200. The signaling and/or contextcontrol block t92200 may distinguish signaling information deliveredfrom the transmitter and deliver the signaling information to the packetstream recovery t92190 such that the signaling information may be mappedto a stream suitable for a context ID.

The RoHC decompressor t92210 may recover headers of packets of a packetstream. When the headers are recovered, the packets of the packet streammay be restored to original IP packets. In other words, the RoHCdecompressor t92210 may perform overhead processing.

The output buffer t92220 may function as a buffer before delivering anoutput stream to an IP layer t92230.

The link layer of the transmitter and the receiver proposed in thepresent invention may include the blocks or modules described above. Inthis way, the link layer may independently operate irrespective of theupper layer and the lower layer, and efficiently perform overheadreduction. In addition, a function which is supportable depending on theupper and lower layers may be easily extended/added/deleted.

FIG. 76 is a diagram illustrating definition according to link layerorganization type according to an embodiment of the present invention.

When a link layer is actually embodied as a protocol layer, a broadcastservice can be transmitted and received through one frequency slot.Here, an example of one frequency slot may be a broadcast channel thatmainly has a specific bandwidth. As described above, according to thepresent invention, in a broadcast system in which a configuration of aphysical layer is changed or in a plurality of broadcast systems withdifferent physical layer configurations, a compatible link layer may bedefined.

The physical layer may have a logical data path for an interface of alink layer. The link layer may access the logical data path of thephysical layer and transmit information associated with thecorresponding data path to the logical data path. The following typesmay be considered as the data path of the physical layer interfaced withthe link layer.

In a broadcast system, a normal data pipe (Normal DP) may exist as atype of data path. The normal data pipe may be a data pipe fortransmission of normal data and may include one or more data pipesaccording to a configuration of a physical layer.

In a broadcast system, a base data pipe (Base DP) may exist as a type ofdata path. The base data pipe may be a data pipe used for specificpurpose and may transmit signaling information (entire or partialsignaling information described in the present invention) and/or commondata in a corresponding frequency slot. As necessary, in order toeffectively manage a bandwidth, data that is generally transmittedthrough a normal data pipe may be transmitted through a base data pipe.When the amount of information to be transmitted when a dedicatedchannel is present exceeds processing capacity of a correspondingchannel, the base data pipe may perform a complementary function. Thatis, data that exceeds the processing capacity of the correspondingchannel may be transmitted through the base data pipe.

In general, the base data pipe continuously uses one designated datapipe. However, one or more data pipes may be dynamically selected forthe base data pipe among a plurality of data pipes using a method suchas physical layer signaling, link layer signaling, or the like in orderto effectively manage a data pipe.

In a broadcast system, a dedicated channel may exist as a type of datapath. The dedicated channel may be a channel used for signaling in aphysical layer or a similar specific purpose and may include a fastinformation channel (FIC) for rapidly acquiring matters that are mainlyserved on a current frequency slot and/or an emergency alert channel(EAC) for immediately transmitting notification of emergency alert to auser.

In general, a logical data path is embodied in a physical layer in orderto transmit the normal data pipe. A logical data path for the base datapipe and/or the dedicated channel may not be embodied in a physicallayer.

A configuration of data to be transmitted in the link layer may bedefined as illustrated in the drawing.

Organization Type 1 may refer to the case in which a logical data pathincludes only a normal data pipe.

Organization Type 2 may refer to the case in which a logical data pathincludes a normal data pipe and a base data pipe.

Organization Type 3 may refer to the case in which a logical data pathincludes a normal data pipe and a dedicated channel.

Organization Type 4 may refer to the case in which a logical data pathincludes a normal data pipe, a data base pipe, and a dedicated channel.

As necessary, the logical data path may include a base data pipe and/ora dedicated channel.

According to an embodiment of the present invention, a transmissionprocedure of signaling information may be determined according toconfiguration of a logical data path. Detailed information of signalingtransmitted through a specific logical data path may be determinedaccording to a protocol of a upper layer of a link layer defined in thepresent invention. Regarding a procedure described in the presentinvention, signaling information parsed through a upper layer may alsobe used and corresponding signaling may be transmitted in the form of anIP packet from the upper layer and transmitted again after beingencapsulated in the form of a link layer packet.

When such signaling information is transmitted, a receiver may extractdetailed signaling information from session information included in anIP packet stream according to protocol configuration. When signalinginformation of a upper layer is used, a database (DB) may be used or ashared memory may be used. For example, in the case of extracting thesignaling information from the session information included in the IPpacket stream, the extracted signaling information may be stored in aDB, a buffer, and/or a shared memory of the receiver. Next, when thesignaling information is needed in a procedure of processing data in abroadcast signal, the signaling information may be obtained from theabove storage device.

FIG. 77 is a diagram illustrating processing of a broadcast signal whena logical data path includes only a normal data pipe according to anembodiment of the present invention.

The diagram illustrates a structure of a link layer when the logical ofthe physical layer includes only a normal data pipe. As described above,the link layer may include a link layer signaling processor, an overheadreduction processor, and an encapsulation (decapsulation) processor.Transmission of information output from each functional module (whichmay be embodied as hardware or software) to an appropriate data path ofthe physical layer may be one of main functions of the link layer.

With regard to an IP stream configured on a upper layer of a link layer,a plurality of packet streams may be transmitted according to a datarate at which data is to be transmitted, and overhead reduction andencapsulation procedures may be performed for each respectivecorresponding packet stream. A physical layer may include a data pipe(DP) as a plurality of logical data paths that a link layer can accessin one frequency band and may transmit a packet stream processed in alink layer for each respective packet stream. When the number of DPs islower than that of packet streams to be transmitted, some of the packetstreams may be multiplexed and input to a DP in consideration of a datarate.

The signaling processor may check transmission system information,related parameters, and/or signaling transmitted in a upper layer andcollect information to be transmitted via signaling. Since only a normaldata pipe is configured in a physical layer, corresponding signalingneeds to be transmitted in the form of packet. Accordingly, signalingmay be indicated using a header, etc. of a packet during link layerpacket configuration. In this case, a header of a packet includingsignaling may include information for identifying whether signaling datais contained in a payload of the packet.

In the case of service signaling transmitted in the form of IP packet ina upper layer, in general, it is possible to process different IPpackets in the same way. However, information of the corresponding IPpacket can be read for a configuration of link layer signaling. To thisend, a packet including signaling may be found using a filtering methodof an IP address. For example, since IANA designates an IP address of224.0.23.60 as ATSC service signaling, the receiver may check an IPpacket having the corresponding IP address use the IP packet forconfiguration of link layer signaling. In this case, the correspondingpacket needs to also be transmitted to a receiver, processing for the IPpacket is performed without change. The receiver may parse an IP packettransmitted to a predetermined IP address and acquire data for signalingin a link layer.

When a plurality of broadcast services are transmitted through onefrequency band, the receiver does not have to decode all DPs, and it isefficient to pre-check signaling information and to decode only a DPassociated with a required service. Accordingly, with regard to anoperation for a link layer of the receiver, the following procedures maybe performed.

When a user selects or changes a service to be received, the receivertunes a corresponding frequency and reads information of the receiver,stored in a DB, etc. with regard to a corresponding channel.

The receiver checks information about a DP that transmits link layersignaling and decodes the corresponding DP to acquire a link layersignaling packet.

The receiver parses the link layer signaling packet and acquiresinformation about a DP that transmits data associated with a serviceselected by the user among one or more DPs transmitted through a currentchannel and overhead reduction information about a packet stream of thecorresponding DP. The receiver may acquire information foridentification of a DP that transmits the data associated with theservice selected by the user from a link layer signaling packet andobtain a corresponding DP based on the information. In addition, thelink layer signaling packet may include information indicating overheadreduction applied to the corresponding DP, and the receiver may restorea DP to which overhead reduction is applied, using the information.

The receiver transmits DP information to be received, to a physicallayer processor that processes a signal or data in a physical layer andreceives a packet stream from a corresponding DP.

The receiver performs encapsulation and header recovery on the packetstream decoded by the physical layer processor.

Then the receiver performs processing according to a protocol of a upperlayer and provides a broadcast service to the user.

FIG. 78 is a diagram illustrating processing of a broadcast signal whena logical data path includes a normal data pipe and a base data pipeaccording to an embodiment of the present invention.

The diagram illustrates a structure of a link layer when the logicaldata path of the physical layer includes a base data pipe and a normaldata pipe. As described above, the link layer may include a link layersignaling part, an overhead reduction part, and an encapsulation(decapsulation) part. In this case, a link layer processor forprocessing a signal and/or data in a link layer may include a link layersignaling processor, an overhead reduction processor, and anencapsulation (decapsulation) processor.

Transmission of information output from each functional module (whichmay be embodied as hardware or software) to an appropriate data path ofthe physical layer may be one of main functions of the link layer.

With regard to an IP stream configured on a upper layer of a link layer,a plurality of packet streams may be transmitted according to a datarate at which data is to be transmitted, and overhead reduction andencapsulation procedures may be performed for each respectivecorresponding packet stream.

A physical layer may include a data pipe (DP) as a plurality of logicaldata paths that a link layer can access in one frequency band and maytransmit a packet stream processed in a link layer for each respectivepacket stream. When the number of DPs is lower than that of packetstreams to be transmitted, some of the packet streams may be multiplexedand input to a DP in consideration of a data rate.

The signaling processor may check transmission system information,related parameters, upper layer signaling, etc. and collect informationto be transmitted via signaling. Since a broadcast signal of thephysical layer includes a base DP and a normal DP, signaling may betransmitted to the base DP and signaling data may be transmitted in theform of packet appropriate for transmission of the base DP inconsideration of a data rate. In this case, signaling may be indicatedusing a header, etc. of a packet during link layer packet configuration.For example, a header of a link layer packet may include informationindicating that data contained in a payload of the packet is signalingdata.

In a physical layer structure in which a logical data path such as abase DP exists, it may be efficient to transmit data that is notaudio/video content, such as signaling information to the base DP inconsideration of a data rate. Accordingly, service signaling that istransmitted in the form of IP packet in a upper layer may be transmittedto the base DP using a method such as IP address filtering, etc. Forexample, IANA designates an IP address of 224.0.23.60 as ATSC servicesignaling, an IP packet stream with the corresponding IP address may betransmitted to the base DP.

When a plurality of IP packet streams about corresponding servicesignaling is present, the IP packet streams may be transmitted to onebase DP using a method such as multiplexing, etc. However, a packetabout different service signaling may be divided into field values suchas a source address and/or a port. In this case, information requiredfor configuration of link layer signaling can also be read from thecorresponding service signaling packet.

When a plurality of broadcast services are transmitted through onefrequency band, the receiver may not have to decode all DPs, maypre-check signaling information, and may decode only a DP that transmitsdata and/or a signal about a corresponding service. Accordingly, thereceiver may perform the following operation with regard to data and/orprocessing in a link layer.

When a user selects or changes a service to be received, the receivertunes a corresponding frequency and reads information of the receiver,stored in a DB, etc. with regard to a corresponding channel. Here, theinformation stored in the DB, etc. may include information foridentification of the base DP.

The receiver decodes the base DP and acquires a link layer signalingpacket included in the base DP.

The receiver parses the link layer signaling packet to acquire DPinformation for reception of the service selected by the user andoverhead reduction information about a packet stream of thecorresponding DP among a plurality of DPs transmitted through a currentchannel and overhead reduction information about a packet stream of thecorresponding DP. The link layer signaling packet may includeinformation for identification of a DP that transmits a signal and/ordata associated with a specific service, and/or information foridentification of a type of overhead reduction applied to a packetstream transmitted to the corresponding DR The receiver may access oneor more DPs or restore the packet included in the corresponding DP usingthe above information.

The receiver is a physical layer processor that processes a signaland/or data according to a protocol of a physical layer, transmitsinformation about a DP to be received for a corresponding service, andreceives a packet stream from the corresponding DP.

The receiver performs decapsulation and header recovery on the packetstream decoded in the physical layer and transmits the packet stream toa upper layer of the receiver in the form of IP packet stream.

Then, the receiver performs processing according to a upper layerprotocol and provides a broadcast service to the user.

In the above-described process of acquiring the link layer packet bydecoding the base DP, information about the base DP (e.g., an identifier(ID) information of the base DP, location information of the base DP, orsignaling information included in the base DP) may be acquired duringprevious channel scan and then stored in a DB and the receiver may usethe stored base DP. Alternatively, the receiver may acquire the base DPby first seeking a DP that the receiver has pre-accessed.

In the above-described process of acquiring the DP information for aservice selected by the user and the overhead reduction informationabout a DP packet stream transmitting the corresponding service, byparsing the link layer packet, if the information about the DPtransmitting the service selected by the user is transmitted throughupper layer signaling (e.g., a layer higher than a link layer, or an IPlayer), the receiver may acquire corresponding information from the DB,the buffer, and/or the shared memory as described above and use theacquired information as information about a DP requiring decoding.

If link layer signaling (link layer signaling information) and normaldata (e.g., broadcast content data) is transmitted through the same DPor if only a DP of one type is used in a broadcast system, the normaldata transmitted through the DP may be temporarily stored in the bufferor the memory while the signaling information is decoded and parsed.Upon acquiring the signaling information, the receiver may transmit acommand for extracting a DP that should be obtained according to thecorresponding signaling information to a device for extracting andprocessing the DP by a method using interior command words of thesystem.

FIG. 79 is a diagram illustrating processing of a broadcast signal whena logical data path includes a normal data pipe and a dedicated channelaccording to an embodiment of the present invention.

The diagram illustrates a structure of a link layer when the logicaldata path of the physical layer includes a dedicated channel and anormal data pipe. As described above, the link layer may include a linklayer signaling part, an overhead reduction part, and an encapsulation(decapsulation) part. In this regard, a link layer processor to beincluded in the receiver may include a link layer signaling processor,an overhead reduction processor, and/or an encapsulation (decapsulation)processor. Transmission of information output from each functionalmodule (which may be embodied as hardware or software) to an appropriatedata path of the physical layer may be one of main functions of the linklayer.

With regard to an IP stream configured on a upper layer of a link layer,a plurality of packet streams may be transmitted according to a datarate at which data is to be transmitted, and overhead reduction andencapsulation procedures may be performed for each respectivecorresponding packet stream. A physical layer may include a data pipe(DP) as a plurality of logical data paths that a link layer can accessin one frequency band and may transmit a packet stream processed in alink layer for each respective packet stream. When the number of DPs islower than that of packet streams to be transmitted, some of the packetstreams may be multiplexed and input to a DP in consideration of a datarate.

The signaling processor may check transmission system information,related parameters, upper layer signaling, etc. and collect informationto be transmitted via signaling. In a physical layer structure in whicha logical data path such as a dedicate channel exists, it may beefficient to mainly transmit signaling information through a dedicatedchannel in consideration of a data rate. However, when a large amount ofdata needs to be transmitted through a dedicated channel, a bandwidthfor the dedicated channel corresponding to the amount of the dedicatedchannel needs to be occupied, and thus it is general to set a high datarate of the dedicated channel. In addition, since a dedicated channel isgenerally received and decoded at higher speed than a DP, it is moreefficient to signaling data in terms of information that needs to berapidly acquired from the receiver. As necessary, when sufficientsignaling data cannot be transmitted through the dedicated channel,signaling data such as the aforementioned link layer signaling packetmay be transmitted through the normal DP, and signaling data transmittedthrough the dedicated channel may include information for identificationof the corresponding link layer signaling packet.

A plurality of dedicated channels may exist as necessary and a channelmay be enable/disable according to a physical layer.

In the case of service signaling transmitted in the form of IP packet ina upper layer, in general, it is possible to process different IPpackets in the same way. However, information of the corresponding IPpacket can be read for a configuration of link layer signaling. To thisend, a packet including signaling may be found using a filtering methodof an IP address. For example, since IANA designates an IP address of224.0.23.60 as ATSC service signaling, the receiver may check an IPpacket having the corresponding IP address use the IP packet forconfiguration of link layer signaling. In this case, the correspondingpacket needs to also be transmitted to a receiver, processing for the IPpacket is performed without change.

When a plurality of IP packet streams about service signaling ispresent, the IP packet streams may be transmitted to one DP togetherwith audio/video data using a method such as multiplexing, etc. However,a packet about service signaling and audio/video data may be dividedinto field values of an IP address, a port, etc.

When a plurality of broadcast services are transmitted through onefrequency band, the receiver does not have to decode all DPs, and it isefficient to pre-check signaling information and to decode only a DPthat transmit signal and/or data associated with a required service.Thus, the receiver may perform processing according to a protocol of alink layer as the following procedure.

When a user selects or changes a service to be received, the receivertunes a corresponding frequency and reads information stored in a DB,etc. with regard to a corresponding channel. The information stored inthe DB may include information for identification of a dedicated channeland/or signaling information for acquisition of channel/service/program.

The receiver decodes data transmitted through the dedicated channel andperforms processing associated with signaling appropriate for purpose ofthe corresponding channel. For example, a dedicated channel fortransmission of FIC may store and update information such as a serviceand/or a channel, and a dedicated channel for transmission of EAC maytransmit emergency alert information.

The receiver may acquire information of DP to be decoded usinginformation transmitted to the dedicated channel. As necessary, whenlink layer signaling is transmitted through a DP, the receiver maypre-decode a DP that transmits signaling and transmit the DP to adedicated channel in order to pre-acquire signaling information. Inaddition, a packet for link layer signaling may be transmitted through anormal DP, and in this case, the signaling data transmitted through thededicated channel may include information for identification of a DPincluding a packet for link layer signaling.

The receiver acquires DP information for reception of a service selectedby a user among a plurality of DPs that are transmitted to a currentchannel and overhead reduction information about a packet stream of thecorresponding DP using the link layer signaling information. The linklayer signaling information may include information for identificationof a DP for transmission of a signal and/or data associated with aspecific service, and/or information for identification of a type ofoverhead reduction applied to a packet stream transmitted to thecorresponding DP. The receiver may access one or more DPs for a specificservice or restore a packet included in the corresponding DP using theinformation.

The receiver transmits information for identification of a DP to bereceived by a physical layer to a physical layer processor thatprocesses a signal and/or data in a physical layer and receives a packetstream from the corresponding DP.

The receiver performs decapsulation and header recovery on a packetstream decoded in a physical layer and transmits the packet stream to aupper layer of the receiver in the form of IP packet stream.

Then the receiver performs processing according to a protocol of a upperlayer and provides a broadcast service to the user.

FIG. 80 is a diagram illustrating processing of a broadcast signal whena logical data path includes a normal data pipe, a base data pipe, and adedicated channel according to an embodiment of the present invention.

The diagram illustrates a structure of a link layer when the logicaldata path of the physical layer includes a dedicated channel, a basedata pipe, and a normal data pipe. As described above, the link layermay include a link layer signaling part, an overhead reduction part, andan encapsulation (decapsulation) part. In this regard, a link layerprocessor to be included in the receiver may include a link layersignaling processor, an overhead reduction processor, and/or anencapsulation (decapsulation) processor. Transmission of informationoutput from each functional module (which may be embodied as hardware orsoftware) to an appropriate data path of the physical layer may be oneof main functions of the link layer.

With regard to an IP stream configured on a upper layer of a link layer,a plurality of packet streams may be transmitted according to a datarate at which data is to be transmitted, and overhead reduction andencapsulation procedures may be performed for each respectivecorresponding packet stream. A physical layer may include a data pipe(DP) as a plurality of logical data paths that a link layer can accessin one frequency band and may transmit a packet stream processed in alink layer for each respective packet stream. When the number of DPs islower than that of packet streams to be transmitted, some of the packetstreams may be multiplexed and input to a DP in consideration of a datarate.

The signaling processor may check transmission system information,related parameters, upper layer signaling, etc. and collect informationto be transmitted via signaling. Since a signal of the physical layerincludes a base DP and a normal DP, it may be efficient to transmitsignaling to the base DP in consideration of a data rate. In this case,the signaling data needs to be transmitted in the form of packetappropriate for transmission through the base DP. Signaling may beindicated using a header, etc. of a packet during link layer packetconfiguration. That is, a header of a link layer signaling packetincluding signaling data may include information indicating thatsignaling data is contained in a payload of the corresponding packet.

In a physical layer structure in which a dedicate channel and a base DPexist simultaneously, signaling information may be divided andtransmitted to the dedicated channel and the base DP. In general, sincea high data rate of the dedicated channel is not set, signalinginformation that has a small amount of signaling and needs to be rapidlyacquired may be transmitted to the dedicated channel and signaling witha high amount of signaling to the base DP. As necessary, a plurality ofdedicated channels may exist and a channel may be enable/disableaccording to a physical layer. In addition, the base DP may beconfigured with a separate structure from a normal DP. In addition, itis possible to designate one of normal DPs and use the normal DP as abase DP.

Service signaling that is transmitted in the form of IP packet in aupper layer may be transmitted to the base DP using a method such as IPaddress filtering, etc. An IP packet stream with a specific IP addressand including signaling information may be transmitted to the base DP.When a plurality of IP packet streams about corresponding servicesignaling is present, the IP packet streams may be transmitted to onebase DP using a method such as multiplexing, etc. A packet aboutdifferent service signaling may be divided into field values such as asource address and/or a port. The receiver may read information requiredfor configuration of the link layer signaling in the correspondingservice signaling packet.

When a plurality of broadcast services are transmitted through onefrequency band, the receiver may not have to decode all DPs, and it maybe efficient to pre-check the signaling information and to decode only aDP that transmits a signal and/or data associated with a requiredservice. Thus, the receiver may perform the following processors asprocessing according to a protocol of a link layer.

When a user selects or changes a service to be received, the receivertunes a corresponding frequency and reads information stored in adatabase DB, etc. with regard to a corresponding channel. Theinformation stored in the DB may include information for identificationof a dedicated channel, information for identification of a base datapipe, and/or signaling information for acquisition ofchannel/service/program.

The receiver decodes data transmitted through the dedicated channel andperforms processing associated with signaling appropriate for purpose ofthe corresponding channel. For example, a dedicated channel fortransmission of FIC may store and update information such as a serviceand/or a channel, and a dedicated channel for transmission of EAC maytransmit emergency alert information.

The receiver may acquire information of the base DP using informationtransmitted to the dedicated channel. The information transmitted to thededicated channel may include information for identification of the baseDP (e.g., an identifier of the base DP and/or an IP address of the baseDP). As necessary, the receiver may update signaling informationpre-stored in a DB of the receiver and related parameters to informationtransmitted in the dedicated channel.

The receiver may decode the base DP and acquire a link layer signalingpacket. As necessary, the link layer signaling packet may be combinedwith signaling information received from the dedicated channel. Thereceiver may find the base DP using the dedicate channel and thesignaling information pre-stored in the receiver.

The receiver acquires DP information for reception of a service selectedby a user among a plurality of DPs that are transmitted to a currentchannel and overhead reduction information about a packet stream of thecorresponding DP using the link layer signaling information. The linklayer signaling information may include information for identificationof a DP for transmission of a signal and/or data associated with aspecific service, and/or information for identification of a type ofoverhead reduction applied to a packet stream transmitted to thecorresponding DP. The receiver may access one or more DPs for a specificservice or restore a packet included in the corresponding DP using theinformation.

The receiver transmits information for identification of a DP to bereceived by a physical layer to a physical layer processor thatprocesses a signal and/or data in a physical layer and receives a packetstream from the corresponding DP.

The receiver performs decapsulation and header recovery on a packetstream decoded in a physical layer and transmits the packet stream to aupper layer of the receiver in the form of IP packet stream.

Then the receiver performs processing according to a protocol of a upperlayer and provides a broadcast service to the user.

According to an embodiment of the present invention, when informationfor service signaling is transmitted by one or more IP packet streams,the IP packet streams may be multiplexed and transmitted as one base DP.The receiver may distinguish between packets for different servicesignaling through a field of a source address and/or a port. Thereceiver may read out information for acquiring/configuring link layersignaling from a service signaling packet.

In the process of processing signaling information transmitted throughthe dedicated channel, the receiver may obtain version information ofthe dedicated channel or information identifying whether update has beenperformed and, if it is judged that there is no change in the signalinginformation in the dedicated channel, the receiver may omit processing(decoding or parsing) of the signaling information transmitted throughthe dedicated channel. If it is confirmed that the dedicated channel hasnot been updated, the receiver may acquire information of a base DPusing prestored information.

In the above-described process of acquiring the DP information for aservice selected by the user and the overhead reduction informationabout the DP packet stream transmitting the corresponding service, ifthe information about the DP transmitting the service selected by theuser is transmitted through upper layer signaling (e.g., a layer higherthan a link layer, or an IP layer), the receiver may acquire thecorresponding information from the DB, the buffer, and/or the sharedmemory as described above and use the acquired information asinformation about a DP requiring decoding.

If link layer signaling (link layer signaling information) and normaldata (e.g., broadcast content data) is transmitted through the same DPor if only type of DP is used in a broadcast system, the normal datatransmitted through the DP may be temporarily stored in the buffer orthe memory while the signaling information is decoded and parsed. Uponacquiring the signaling information, the receiver may transmit a commandfor extracting a DP that should be obtained according to thecorresponding signaling information to a device for extracting andprocessing the DP by a method using system interior command words.

FIG. 81 is a diagram illustrating a detailed processing operation of asignal and/or data in a link layer of a receiver when a logical datapath includes a normal data pipe, a base data pipe, and a dedicatedchannel according to an embodiment of the present invention.

The present embodiment considers a situation in which one or moreservices provided by one or more broadcasters are transmitted in onefrequency band. It may be considered that one broadcaster transmits oneor more broadcast services, one service includes one or more componentsand a user receives content in units of broadcast services. In addition,some of one or more components included in one broadcast service may bereplaced with other components according to user selection.

A fast information channel (FIC) and/or emergency alert channel (EAC)may be transmitted to a dedicated channel. A base DP and a normal DP maybe differentiated in a broadcast signal and transmitted or managed.Configuration information of the FIC and/or the EAC may be transmittedthrough physical layer signaling so as to notify the receiver of the FICand/or the EAC, and the link layer may format signaling according to thecharacteristic of the corresponding channel. Transmission of data to aspecific channel of a physical layer is performed from a logical pointof view and an actual operation may be performed according to thecharacteristic of a physical layer.

Information about a service of each broadcaster, transmitted in acorresponding frequency, and information about a path for reception ofthe service may be transmitted through the FTC. To this end, thefollowing information may be provided (signaled) via link layersignaling.

System Parameter: Transmitter related parameter, and/or parameterrelated to a broadcaster that provides a service in a correspondingchannel.

Link layer: which includes context information associated with IP headercompression and/or ID of a DP to which corresponding context is applied.

Upper layer: IP address and/or UDP port number, service and/or componentinformation, emergency alert information, and mapping relationinformation between a DP and an IP address of a packet streamtransmitted in an IP layer.

When a plurality of broadcast services is transmitted through onefrequency band, a receiver may not have to decode all DPs, and it may beefficient to pre-check signaling information and to decode only a DPabout a required service. In a broadcast system, a transmitter maytransmit information for identification of only a required DP through anFIC, and the receiver may check a DP to be accessed for a specificserviced, using the FIC. In this case, an operation associated with thelink layer of the receiver may be performed as follows.

When a user selects or changes a service to be received by a user, thereceiver tunes a corresponding frequency and reads information of areceiver, stored in a DB, etc. in regard to a corresponding channel. Theinformation stored in the DB of the receiver may be configured byacquiring an FIC during initial channel scan and using informationincluded in the FIC.

The receiver may receive an FIC and update a pre-stored DB or acquireinformation about a component about a service selected by the user andinformation about a mapping relation for DPs that transmit componentsfrom the FIC. In addition, the information about a base DP thattransmits signaling may be acquired from the FIC.

When initialization information related to robust header compression(RoHC) is present in signaling transmitted through the FIC, the receivermay acquire the initialization information and prepare header recovery.

The receiver decodes a base DP and/or a DP that transmits a serviceselected by a user based on information transmitted through the FIC.

The receiver acquires overhead reduction information about a DP that isbeing received, included in the base DP, performs decapsulation and/orheader recovery on a packet stream received in a normal DP using theacquired overhead information, and transmits the packet stream to aupper layer of the receiver in the form of IP packet stream.

The receiver may receive service signaling transmitted in the form of IPpacket with a specific address through a base DP and transmit the packetstream to the upper layer with regard to a received service.

When emergency alert occurs, in order to rapidly transmit an emergencyalert message to a user, the receiver receives signaling informationincluded in a CAP message through signaling, parses the signalinginformation, and immediately transmits the signaling information to auser, and finds a path for reception of a corresponding service andreceives service data when information of a path through which anaudio/video service can be received via signaling can be confirmed. Inaddition, when information transmitted through a broadband and so on ispresent, an NRT service and additional information are received usingcorresponding uniform resource identifier (URI) information and so on.Signaling information associated with emergency alert will be describedbelow in detail.

The receiver processes the emergency alert as follows.

The receiver recognizes a situation in which an emergency alert messageis transmitted through a preamble and so on of a physical layer. Thepreamble of the physical layer may be a signaling signal included in abroadcast signal and may correspond to signaling in the physical layer.The preamble of the physical layer may mainly include information foracquisition of data, a broadcast frame, a data pipe, and/or atransmission parameter that are included in a broadcast signal.

The receiver checks configuration of an emergency alert channel (EAC)through physical layer signaling of the receiver and decodes the EAC toacquire EAT. Here, the EAC may correspond to the aforementioneddedicated channel.

The receiver checks the received EAT, extracts a CAP message, andtransmits the CAP message to a CAP parser.

The receiver decodes a corresponding DP and receives service data whenservice information associated with the emergency alert is present inthe EAT. The EAT may include information for identification of a DP fortransmitting a service associated with the emergency alert.

When information associated with NRT service data is present in the EATor the CAP message, the receiver receives the information through abroadband.

FIG. 82 is a diagram illustrating syntax of a fast information channel(FIC) according to an embodiment of the present invention.

Information included in the FIC may be transmitted in the form of fastinformation table (FIT).

Information included in the FIT may be transmitted in the form of XMLand/or section table.

The FIT may include table_id information, FIT_data_version information,num_broadcast information, broadcast_id information, delivery_system_idinformation, base_DP_id information, base_DP_version information,num_service information, service_id information, service_categoryinformation, service_hidden_flag information, SP_indicator information,num_component information, component_id information, DP_id information,context_id information, RoHC_init_descriptor, context_profileinformation, max_cid information, and/or large_cid information.

The table_id information indicates that a corresponding table sectionrefers to fast information table.

The FIT_data_version information may indicate version information aboutsyntax and semantics contained in the fast information table. Thereceiver may determine whether signaling contained in the correspondingfast information table is processed, using the FIT_data_versioninformation. The receiver may determine whether information ofpre-stored FIC is updated, using the information.

The num_broadcast information may indicate the number of broadcastersthat transmit a broadcast service and/or content through a correspondingfrequency or a transmitted transport frame.

The broadcast_id information may indicate a unique identifier of abroadcaster that transmits a broadcast service and/or content through acorresponding frequency or a transmitted transport frame. In the case ofa broadcaster that transmits MPEG-2 TS-based data, broadcast_id may havea value such as transport_stream_id of MPEG-2 TS.

The delivery_system_id information may indicate an identifier for abroadcast transmission system that applies and processes the sametransmission parameter on a broadcast network that performstransmission.

The base_DP_id information is information for identification of a baseDP in a broadcast signal. The base DP may refer to a DP that transmitsservice signaling including overhead reduction and/or program specificinformation/system information (PSI/SI) of a broadcaster correspondingto broadcast_id. Alternatively, the base_DP_id information may refer toa representative DP that can decode a component included in a broadcastservice in the corresponding broadcaster.

The base_DP_version information may refer to version information aboutdata transmitted through a base DP. For example, when service signalingsuch as PSI/SI and so on is transmitted through the base DP, if servicesignaling is changed, a value of the base_DP_version information may beincreased one by one.

The num_service information may refer to the number of broadcastservices transmitted from a broadcaster corresponding to thebroadcast_id in a corresponding frequency or a transport frame.

The service_id information may be used as an identifier foridentification of a broadcast service.

The service_category information may refer to a category of a broadcastservice. According to a value of a corresponding field, theservice_category information may have the following meaning. When avalue of the service_category information is 0x01, the service_categoryinformation may refer to a basic TV, when the value of theservice_category information is 0x02, the service_category informationmay refer to a basic radio, when the value of the service_categoryinformation is 0x03, the service_category information may refer to an RIservice, when the value of the service_category information is 0x08, theservice_category information may refer to a service guide, and when thevalue of the service_category information is 0x09, the service_categoryinformation may refer to emergency alerting.

The service_hidden_flag information may indicate whether a correspondingbroadcast service is hidden. When the service is hidden, the broadcastservice may be a test service or a self-used service and may beprocessed to be disregarded or hidden from a service list by a broadcastreceiver.

The SP_indicator information may indicate whether service protection isapplied to one or more components in a corresponding broadcast service.

The num_component information may indicate the number of componentsincluded in a corresponding broadcast service.

The component_id information may be used as an identifier foridentification of a corresponding component in a broadcast service.

The DP_id information may be used as an identifier indicating a DP thattransmits a corresponding component.

The RoHC_init_descriptor may include information associated withoverhead reduction and/or header recovery. The RoHC_init_descriptor mayinclude information for identification of a header compression methodused in a transmission terminal.

The context_id information may represent a context corresponding to afollowing RoHC related field. The context_id information may correspondto a context identifier (CID).

The context_profile information may represent a range of a protocol forcompression of a header in RoHC. When a compressor and a decompressorhave the same profile, it is possible to compress and restore a streamin the RoHC.

The max_cid information is used for indicating a maximum value of a CIDto a decompressor.

The large_cid information has a boolean value and indicates whether ashort CID (0 to 15) or an embedded CID (0 to 16383) is used for CIDconfiguration. Accordingly, the sized of byte for representing the CIDis determined together.

FIG. 83 is a diagram illustrating syntax of an emergency alert table(EAT) according to an embodiment of the present invention.

Information associated with emergency alert may be transmitted throughthe EAC. The EAC may correspond to the aforementioned dedicated channel.

The EAT according to an embodiment of the present invention may includeEAT_protocol_version information, automatic_tuning_flag information,num_EAS_messages information, EAS_message_id information,EAS_IP_version_flag information, EAS_message_transfer_type information,EAS_message_encoding_type information, EAS_NRT_flag information,EAS_message_length information, EAS_message_byte information, IP_addressinformation, UDP_port_num information, DP_id information,automatic_tuning_channel_number information, automatic_tuning_DP_idinformation, automatic_tuning_service_id information, and/orEAS_NRT_service_id information.

The EAT_protocol_version information indicates a protocol version ofreceived EAT.

The automatic_tuning_flag information indicates whether a receiverautomatically performs channel conversion.

The num_EAS_messages information indicates the number of messagescontained in the EAT.

The EAS_message_id information is information for identification of eachEAS message.

The EAS_IP_version_flag information indicates IPv4 when a value of theEAS_IP_version_flag information is 0, and indicates IPv6 when a value ofthe EAS_IP_version_flag information is 1.

The EAS_message_transfer_type information indicates the form in which anEAS message is transmitted. When a value of theEAS_message_transfer_type information is 000, theEAS_message_transfer_type information indicates a not specified state,when a value of the EAS_message_transfer_type information is 001, theEAS_message_transfer_type information indicates a no alert message (onlyAV content), and when a value of the EAS_message_transfer_typeinformation is 010, the EAS_message_transfer_type information indicatesthat an EAS message is contained in corresponding EAT. To this end, alength field and a field about the corresponding EAS message are added.When a value of the EAS_message_transfer_type information is 011, theEAS_message_transfer_type information indicates that the EAS message istransmitted through a data pipe. The EAS may be transmitted in the formof IP datagram in a data pipe. To this end, IP address, UDP portinformation, and DP information of a transmitted physical layer may beadded.

The EAS_message_encoding_type information indicates information about anencoding type of an emergence alert message. For example, when a valueof the EAS_message_encoding_type information is 000, theEAS_message_encoding_type information indicates a not specific state,when a value of the EAS_message_encoding_type information is 001, theEAS_message_encoding_type information indicates No Encoding, when avalue of the EAS_message_encoding_type information is 010, theEAS_message_encoding_type information indicates DEFLATE algorithm(RFC1951), and 001 to 111 among values of the EAS_message_encoding_typeinformation may be reserved for other encoding types.

The EAS_NRT_flag information indicates whether NRT contents and/or NRTdata_associated with a received message is present. When a value of theEAS_NRT_flag information is 0, the EAS_NRT_flag information indicatesthat NRT contents and/or NRT data associated with a received emergencymessage is not present, and when a value of the EAS_NRT_flag informationis 1, the EAS_NRT_flag information indicates that NRT contents and/orNRT data associated with a received emergency message is present.

The EAS_message_length information indicates a length of an EAS message.

The EAS_message_byte information includes content of an EAS message.

The IP_address information indicates an IP address of an IP address fortransmission of an EAS message.

The UDP_port_num information indicates a UDP port number fortransmission of an EAS message.

The DP_id information identifies a data pipe that transmits an EASmessage.

The automatic_tuning_channel_number information includes informationabout a number of a channel to be converted.

The automatic_tuning_DP_id information is information for identificationof a data pipe that transmits corresponding content.

The automatic_tuning_service_id information is information foridentification of a service to which corresponding content belongs.

The EAS_NRT_service_id information is information for identification ofan NRT service corresponding to the case in which NRT contents and dataassociated with a received emergency alert message and transmitted, thatis, the case in which an EAS_NRT_flag is enabled.

FIG. 84 is a diagram illustrating a packet transmitted to a data pipeaccording to an embodiment of the present invention.

According to an embodiment of the present invention, configuration of apacket in a link layer is newly defined so as to generate a compatiblelink layer packet irrespective of change in protocol of a upper layer orthe link layer or a lower layer of the link layer.

The link layer packet according to an embodiment of the presentinvention may be transmitted to a normal DP and/or a base DP.

The link layer packet may include a fixed header, an expansion header,and/or a payload.

The fixed header is a header with a fixed size and the expansion headeris a header, the size of which can be changed according to configurationof the packet of the upper layer. The payload is a region in which dataof the upper layer is transmitted.

A header (the fixed header or the expansion header) of a packet mayinclude a field indicating a type of the payload of the packet. In thecase of the fixed header, first 3 bits (packet type) of 1 byte mayinclude data for identification of a packet type of the upper layer, andthe remaining 5 bits may be used as an indicator part. The indicatorpart may include data for identification of a configuring method of apayload and/or configuration information of the expansion header and maybe changed according to a packet type.

A table shown in the diagram represents a type of a upper layer includedin a payload according to a value of a packet type.

According to system configuration, an IP packet and/or an RoHC packet ofthe payload may be transmitted through a DP, and a signaling packet maybe transmitted through a base DP. Accordingly, when a plurality ofpackets are mixed and transmitted, packet type values may also beapplied so as to differentiate a data packet and a signaling packet.

When a packet type value is 000, an IP packet of IPv4 is included in apayload.

When a packet type value is 001, an IP packet of IPv6 is included in apayload.

When a packet type value is 010, a compressed IP packet is included in apayload. The compressed IP packet may include an IP packet to whichheader compression is applied.

When a packet type value is 110, a packet including signaling data isincluded in a pay load.

When a packet type value is 111, a framed packet type is included in apayload.

FIG. 85 is a diagram illustrating a detailed processing operation of asignal and/or data in each protocol stack of a transmitter when alogical data path of a physical layer includes a dedicated channel, abase DP, and a normal data DP, according to another embodiment of thepresent invention.

In one frequency band, one or more broadcasters may provide broadcastservices. A broadcaster transmits multiple broadcast services and onebroadcast service may include one or more components. A user may receivecontent in units of broadcast services.

In a broadcast system, a session-based transmission protocol may be usedto support IP hybrid broadcast and the contents of signaling deliveredto each signaling path may be determined according to the structure ofthe corresponding transmission protocol.

As described above, data related to the FIC and/or the EAC may betransmitted/received over the dedicated channel. In the broadcastsystem, a base DP and a normal DP may be used to distinguishtherebetween.

Configuration information of the FIC and/or EAC may be included inphysical layer signaling (or a transmission parameter). A link layer mayformat signaling according to characteristics of a correspondingchannel. Transmission of data to a specific channel of a physical layermay be performed from a logical point of view and actual operation maybe performed according to characteristics of a physical layer.

The FIC may include information about services of each broadcaster,transmitted in a corresponding frequency and information about paths forreceiving the services. The FIC may include information for serviceacquisition and may be referred to as service acquisition information.

The FIC and/or the EAC may be included in link layer signaling.

Link layer signaling may include the following information.

System Parameter—A parameter related to a transmitter or a parameterrelated to a broadcaster that provides a service in a correspondingchannel.

Link layer: Context information associated with IP header compressionand an ID of a DP to which a corresponding context is applied.

Upper layer: IP address and UDP port number, service and componentinformation, emergency alert information, and a mapping relationshipbetween an ID address, a UDP port number, a session ID, and a DP of apacket stream and signaling transmitted in an IP layer.

As described above, one or more broadcast services are transmitted inone frequency band, the receiver does not need to decode all DPs and itis efficient to pre-check signaling information and to decode only a DPrelated to a necessary service.

In this case, referring to the drawing, the broadcast system may provideand acquire information for mapping a DP and a service, using the FICand/or the base DP.

A process of processing a broadcast signal or broadcast data in atransmitter of the drawing will now be described. One or morebroadcasters (broadcasters #1 to #N) may process component signalingand/or data for one or more broadcast services so as to be transmittedthrough one or more sessions. One broadcast service may be transmittedthrough one or more sessions. The broadcast service may include one ormore components included in the broadcast service and/or signalinginformation for the broadcast service. Component signaling may includeinformation used to acquire components included in the broadcast servicein a receiver. Service signaling, component signaling, and/or data forone or more broadcast services may be transmitted to a link layerthrough processing in an IP layer.

In the link layer, the transmitter performs overhead reduction whenoverhead reduction for an IP packet is needed and generates relatedinformation as link layer signaling. Link layer signaling may include asystem parameter specifying the broadcast system, in addition to theabove-described information. The transmitter may process an IP packet ina link layer processing procedure and transmit the processed IP packetto a physical layer in the form of one or more DPs.

The transmitter may transmit link layer signaling to the receiver in theform or configuration of an FIC and/or an EAC. Meanwhile, thetransmitter may also transmit link layer signaling to the base DPthrough an encapsulation procedure of the link layer.

FIG. 86 is a diagram illustrating a detailed processing operation of asignal and/or data in each protocol stack of a receiver when a logicaldata path of a physical layer includes a dedicated channel, a base DP,and a normal data DP, according to another embodiment of the presentinvention.

If a user selects or changes a service desired to be received, areceiver tunes to a corresponding frequency. The receiver readsinformation stored in a DB etc. in association with a correspondingchannel. The information stored in the DB etc. of the receiver may beinformation included upon acquiring an FIC and/or an EAC during initialchannel scan. Alternatively, the receiver may extract transmittedinformation as described above in this specification.

The receiver may receive the FIC and/or the EAC, receive informationabout a channel that the receiver desires to access, and then updateinformation pre-stored in the DB. The receiver may acquire componentsfor a service selected by a user and information about a mappingrelationship of a DP transmitted by each component or acquire a base DPand/or a normal DP through which signaling necessary to obtain suchinformation is transmitted. Meanwhile, when it is judged that there isno change in corresponding information using version information of theFIC or information identifying whether to require additional update of adedicated channel, the receiver may omit a procedure of decoding orparsing the received FIC and/or EAC.

The receiver may acquire a link layer signaling packet including linklayer signaling information by decoding a base DP and/or a DP throughwhich signaling information is transmitted, based on informationtransmitted through the FIC. The receiver may use, when necessary, thereceived link layer signaling information by a combination withsignaling information (e.g., receiver information in the drawing)received through the dedicated channel.

The receiver may acquire information about a DP for receiving a serviceselected by the user among multiple DPs that are being transmitted overa current channel and overhead reduction information about a packetstream of the corresponding DP, using the FIC and/or the link layersignaling information.

When the information about the DP for receiving the selected service istransmitted through upper layer signaling, the receiver may acquiresignaling information stored in the DB and/or the shared memory asdescribed above and then acquire information about a DP to be decoded,indicated by the corresponding signaling information.

When the link layer signaling information and normal data (e.g., dataincluded in broadcast content) are transmitted through the same DP oronly one DP is used for transmission of the link layer signalinginformation and normal data, the receiver may temporarily store thenormal data transmitted through the DP in a device such as a bufferwhile the signaling information is decoded and/or parsed.

The receiver may acquire the base DP and/or the DP through which thesignaling information is transmitted, acquire overhead reductioninformation about a DP to be received, perform decapsulation and/orheader recovery for a packet stream received in a normal DP, using theacquired overhead information, process the packet stream in the form ofan IP packet stream, and transmit the IP packet stream to a upper layerof the receiver.

FIG. 87 is a diagram illustrating a syntax of an FIC according toanother embodiment of the present invention.

Information included in the FIC described in this drawing may beselectively combined with other information included in the FIC and mayconfigure the FIC.

The receiver may rapidly acquire information about a channel, using theinformation included in the FIC. The receiver may acquire bootstraprelated information using the information included in the FIC. The FICmay include information for fast channel scan and/or fast serviceacquisition. The FIC may be referred to by other names, for example, aservice list table or service acquisition information. The FIC may betransmitted by being included in an IP packet in an IP layer accordingto a broadcast system. In this case, an IP address and/or a UDP portnumber, transmitting the FIC, may be fixed to specific values and thereceiver may recognize that the IP packet transmitted with thecorresponding IP address and/or UDP port number includes the FIC,without an additional processing procedure.

The FIC may include FIC_protocol_version information,transport_stream_id information, num_partitions information,partition_id information, partition_protocol_version information, numservices information, service id information, service_data_versioninformation, service_channel_number information, service_categoryinformation, service_status information, service_distributioninformation, sp_indicator information, IP_version_flag information,SSC_source_IP_address_flag information, SSC_source_IP_addressinformation, SSC_destination_IP_address information,SSC_destination_UDP_port information, SSC_TSI information, SSC_DP_IDinformation, num_partition_level_descriptors information,partition_level_descriptor( ) information, num_FIC_level_descriptorsinformation, and/or FIC_level_descriptor( ) information.

FIC_protocol_version information represents a version of a protocol ofan FIC.

transport_stream_id information identifies a broadcast stream.transport_stream_id information may be used as information foridentifying a broadcaster.

num_partitions information represents the number of partitions in abroadcast stream. The broadcast stream may be transmitted after beingdivided into one or more partitions. Each partition may include one ormore DPs. The DPs included in each partition may be used by onebroadcaster. In this case, the partition may be defined as a datatransmission unit allocated to each broadcaster.

partition_id information identifies a partition. partition_idinformation may identify a broadcaster.

partition_protocol_version information represents a version of aprotocol of a partition.

num_services information represents the number of services included in apartition.

A service may include one or more components.

service_id information identifies a service.

service_data_version information represents change when a signalingtable (signaling information) for a service is changed or a serviceentry for a service signaled by an FIC is changed. service_data_versioninformation may increment a value thereof whenever such change ispresent.

service_channel_number information represents a channel number of aservice.

service_category information represents a category of a service. Thecategory of a service includes A/V content, audio content, an electronicservice guide (ESG), and/or content on demand (CoD).

service_status information represents a state of a service. A state of aservice may include an active or suspended state and a hidden or shownstate. The state of a service may include an inactive state. In theinactive state, broadcast content is not currently provided but may beprovided later. Accordingly, when a viewer scans a channel in areceiver, the receiver may not show a scan result for a correspondingservice to the viewer.

service_distribution information represents a distribution state of datafor a service. For example, service_distribution information mayrepresent that entire data of a service is included in one partition,partial data of a service is not included in a current partition butcontent is presentable only by data in this partition, another partitionis needed to present content, or another broadcast stream is needed topresent content.

sp_indicator information identifies whether service protection has beenapplied. sp_indicator information may identify, for example, formeaningful presentation, whether one or more necessary components areprotected (e.g., a state in which a component is encrypted).

IP_version_flag information identifies whether an IP address indicatedby SSC_source_IP_address information and/or SSC destination IP addressinformation is an IPv4 address or an IPv6 address.

SSC_source_IP_address_flag information identifies whetherSSC_source_IP_address information is present.

SSC_source_IP_address information represents a source IP address of anIP datagram that transmits signaling information for a service. Thesignaling information for a service may be referred to as service layersignaling. Service layer signaling includes information specifying abroadcast service. For example, service layer signaling may includeinformation identifying a data unit (a session, a DP, or a packet) thattransmits components constituting a broadcast service.

SSC_destination_IP_address information represents a destination IPaddress of an IP datagram (or channel) that transmits signalinginformation for a service.

SSC_destination_UDP_port information represents a destination UDP portnumber for a UDP/IP stream that transmits signaling information for aservice.

SSC_TSI information represents a transport session identifier (TSI) ofan LCT channel (or session) that transmits signaling information (or asignaling table) for a service.

SSC_DP_ID information represents an ID for identifying a DP includingsignaling information (or a signaling table) for a service. As a DPincluding the signaling information, the most robust DP in a broadcasttransmission process may be allocated.

num_partition_level_descriptors information identifies the number ofdescriptors of a partition level for a partition.

partition_level_descriptor( ) information includes zero or moredescriptors that provide additional information for a partition.

num_FIC_level_descriptors information represents the number ofdescriptors of an FIC level for an FIC.

FIC_level_descriptor( ) information includes zero or more descriptorsthat provide additional information for an FIC.

FIG. 88 is a diagram illustrating signaling_Information_Part( )according to an embodiment of the present invention.

A broadcast system may add additional information to an extended headerpart in the case of a packet for transmitting signaling information in astructure of a packet transmitted through the above-described DP. Suchadditional information will be referred to asSignaling_Information_Part( ).

Signaling_Information_Part( ) may include information used to determinea processing module (or processor) for received signaling information.In a system configuration procedure, the broadcast system may adjust thenumber of fields indicating information and the number of bits allocatedto each field, in a byte allocated to Signaling_Information_Part( ).When signaling information is transmitted through multiplexing, areceiver may use information included in Signaling_Information_Part( )to determine whether corresponding signaling information is processedand determine to which signaling processing module signaling informationshould be transmitted.

Signaling_Information_Part( ) may include Signaling_Class information,Information_Type information, and/or signaling format information.

Signaling_Class information may represent a class of transmittedsignaling information. Signaling information may correspond to an FIC,an EAC, link layer signaling information, service signaling information,and/or upper layer signaling information. Mapping for a class ofsignaling information indicated by each value of configuration of thenumber of bits of a field of Signaling_Class information may bedetermined according to system design.

Information_Type information may be used to indicate details ofsignaling information identified by signaling class information. Meaningof a value indicated by Information_Type information may be additionallydefined according to class of signaling information indicated bySignaling_Class information.

Signaling format information represents a form (or format) of signalinginformation configured in a payload. The signaling format informationmay identify formats of different types of signaling informationillustrated in the drawing and identify a format of additionallydesignated signaling information.

Signaling_Information_Part( ) of (a) and (b) illustrated in the drawingis one embodiment and the number of bits allocated to each field thereofmay be adjusted according to characteristics of the broadcast system.

Signaling_Information_Part( ) as in (a) of the drawing may includesignaling class information and/or signaling format information.Signaling_Information_Part( ) may be used when a type of signalinginformation need not be designated or an information type can be judgedin signaling information. Alternatively, when only one signaling formatis used or when an additional protocol for signaling is present so thatsignaling formats are always equal, only a 4-bit signaling class fieldmay be used without configuring a signaling field and the other fieldsmay be reserved for later use or an 8-bit signaling class maybeconfigured to support various types of signaling.

Signaling_Information_Part( ) as in (b) of the drawing may furtherinclude information type information for indicating a type orcharacteristic of more detailed information in a signaling class whenthe signaling class is designated and may also include signaling formatinformation. Signaling class information and information typeinformation may be used to determine decapsulation of signalinginformation or a processing procedure of corresponding signaling. Adetailed structure or processing of link layer signaling may refer tothe above description and a description which will be given below.

FIG. 89 is a diagram illustrating a procedure for controlling anoperation mode of a transmitter and/or a receiver in a link layeraccording to an embodiment of the present invention.

When the operation mode of the transmitter or the receiver of the linklayer is determined, a broadcast system can be more efficiently used andcan be flexibly designed. The method of controlling the link layer modeproposed according to the present invention can dynamically convert amode of a link layer in order to efficiently manage a system bandwidthand processing time. In addition, the method of controlling the linklayer mode according to the present invention may easily cope with thecase in which a specific mode needs to be supported due to change in aphysical layer or on the other hand, the specific mode does not have tobe changed any more. In addition, the method of controlling the linklayer mode according to the present invention may also allow a broadcastsystem to easily satisfy requirements of a corresponding broadcasterwhen a broadcaster providing a broadcast service intends to designate amethod of transmitting a corresponding service.

The method of controlling the mode of the link layer may be configuredto be performed only in a link layer or to be performed via change indata configuration in the link layer. In this case, it is possible toperform an independent operation of each layer in a network layer and/ora physical layer without embodiment of a separate function. In the modeof the link layer proposed according to the present invention, it ispossible to control the mode with signaling or parameters in a systemwithout changing a system in order to satisfy configuration of aphysical layer. A specific mode may be performed only when processing ofcorresponding input is supported in a physical layer.

The diagram is a flowchart illustrating processing of signal and/or datain an IP layer, a link layer, and a physical layer by a transmitterand/or a receiver.

A function block (which may be embodied as hardware and/or software) formode control may be added to the link layer and may manage parameterand/or signaling information for determination of whether a packet isprocessed. The link layer may determine whether a corresponding functionis performed during processing of a packet stream using information of amode control functional block.

First, an operation of the transmitter will be described.

When an IP is input to a link layer, the transmitter determines whetheroverhead reduction (j16020) is performed using a mode control parameter(j16005). The mode control parameter may be generated by a serviceprovider in the transmitter. The mode control parameter will bedescribed below in detail.

When the overhead reduction (j16020) is performed, information aboutoverhead reduction is generated and is added to link layer signaling(j16060) information. The link layer signaling (j16060) information mayinclude all or some of mode control parameters. The link layer signaling(j16060) information may be transmitted in the form of link layersignaling packet. The link layer signaling packet may be mapped to a DPand transmitted to the receiver, but may not be mapped to the DP and maybe transmitted to the receiver in the form of link layer signalingpacket through a predetermined region of a broadcast signal.

A packet stream on which the overhead reduction (j16020) is performed isencapsulated (j16030) and input to a DP of a physical layer (j16040).When overhead reduction is not performed, whether encapsulation isperformed is re-determined (j16050).

A packet stream on which the encapsulation (j16030) is performed isinput to a DP (j16040) of a physical layer. In this case, the physicallayer performs an operation for processing a general packet (a linklayer packet). When overhead reduction and encapsulation are notperformed, an IP packet is transmitted directly to a physical layer. Inthis case, the physical layer performs an operation for processing theIP packet. When the IP packet is directly transmitted, a parameter maybe applied to perform the operation only when the physical layer supportIP packet input. That is, a value of a mode control parameter may beconfigured to be adjusted such that a process of transmitting an IPpacket directly to a physical layer is not performed when the physicallayer does not support processing of an IP packet.

The transmitter transmits a broadcast signal on which this process isperformed, to the receiver.

An operation of the receiver will be described below.

When a specific DP is selected for the reason such channel change and soon according to user manipulation and a corresponding DP receives apacket stream (j16110), the receiver may check a mode in which a packetis generated, using a header and/or signaling information of the packetstream (j16120). When the operation mode during transmission of thecorresponding DP is checked, decapsulation (j16130) and overheadreduction (j16140) processes are performed through a receiving operatingprocess of a link layer and then an IP packet is transmitted to an upperlayer. The overhead reduction (j16140) process may include an overheadrecovery process.

FIG. 90 is a diagram illustrating an operation in a link layer accordingto a value of a flag and a type of a packet transmitted to a physicallayer according to an embodiment of the present invention.

In order to determine an operation mode of the link layer, theaforementioned signaling method may be used. Signaling informationassociated with the method may be transmitted directly to a receiver. Inthis case, the aforementioned signaling data or link layer signalingpacket may include mode control that will be described below and relatedinformation.

In consideration of the complexity of the receiver, an operation mode ofthe link layer may be indirectly indicated to the receiver.

The following two flags may be configured with regard to control of anoperation mode.

-   -   Header compression flag (HCF): This may be a flag for        determination of whether header compression is applied to a        corresponding link layer and may have a value indicating enable        or disable.    -   Encapsulation flag (EF): This may be a flag for determination of        whether encapsulation is applied in a corresponding link layer        and may have a value indicating enable or disable. However, when        encapsulation needs to be performed according to a header        compression scheme, the EF may be defined to be dependent upon a        HCF.

A value mapped to each flag may be applied according to systemconfiguration as long as the value represents Enable and Disable, and abit number allocated to each flag can be changed. According to anembodiment of the present invention, an enable value may be mapped to 1and a disable value may be mapped to 0.

The diagram shows whether header compression and encapsulation includedin a link layer are performed according to values of HCF and EF and inthis case, a packet format transmitted to a physical layer. That is,according to an embodiment of the present invention, the receiver canknow a type of a packet input to the physical layer as information aboutthe HCF and the EF.

FIG. 91 is a diagram a descriptor for signaling a mode control parameteraccording to an embodiment of the present invention.

Flags as information about mode control in a link layer may be signalinginformation, generated by the transmitter in the form of descriptor, andtransmitted to the receiver. Signaling including a flag as informationabout mode control may be used to control an operation mode in atransmitter of a headend terminal, and whether a flag as informationabout mode control is included in signaling transmitted to the receivermay be optionally selected.

When signaling including a flag as information about mode control istransmitted to the receiver, the receiver may directly select anoperation mode about a corresponding DP and perform a packetdecapsulation operation. When signaling including a flag as informationabout mode control is not transmitted to the receiver, the receiver candetermine a mode in which the signaling is transmitted, using physicallayer signaling or field information of a packet header, which istransmitted to the receiver.

The link layer mode control description according to an embodiment ofthe present invention may include DP_id information, HCF information,and/or EF information. The link layer mode control description may beincluded in a transmission parameter in the aforementioned FIC, linklayer signaling packet, signaling via a dedicated channel, PSI/SI,and/or physical layer.

The DP_id information identifies a DP to which a mode in a link layer isapplied.

The HCF information identifies whether header compression is applied inthe DP identified by the DP_id information.

The EF information identifies whether encapsulation is performed on theDP identified by the DP_id information.

FIG. 92 is a diagram illustrating an operation of a transmitter forcontrolling a operation mode according to an embodiment of the presentinvention.

Although not illustrated in the diagram, prior to a processing processof al ink layer, a transmitter may perform processing in a upper layer(e.g., an IP layer). The transmitter may generate an IP packet includingbroadcast data for a broadcast service.

The transmitter parses or generates a system parameter (JS19010). Here,the system parameter may correspond to the aforementioned signaling dataand signaling information.

The transmitter may receive or set mode control related parameter orsignaling information during a broadcast data processing process in alink layer and sets a flag value associated with operation mode control(JS19020). The transmitter may perform this operation after the headercompression operation or the encapsulation operation. That is, thetransmitter may perform the header compression or encapsulationoperation and generate information associated with this operation.

The transmitter acquires a packet of a upper layer that needs to betransmitted through a broadcast signal (JS19030). Here, the packet ofthe upper layer may correspond to an IP packet.

The transmitter checks HCF in order to determine whether headercompression is applied to the packet of the upper layer (JS19040).

When the HCF is enabled, the transmitter applies the header compressionto the packet of the upper layer (JS19050). After header compression isperformed, the transmitter may generate the HCF. The HCF may be used tosignal whether header compression is applied, to the receiver.

The transmitter performs encapsulation on the packet of the upper layerto which header compression is applied to generate a link layer packet(JS19060). After the encapsulation process is performed, the transmittermay generate an EF. The EF may be used to signal whether encapsulationis applied to the upper layer packet, to the receiver.

The transmitter transmits the link layer packet to a physical layerprocessor (JS19070). Then the physical layer processor generates abroadcast signal including the link layer packet and transmits thebroadcast signal to the receiver.

When the HCF is disabled, the transmitter checks the EF in order todetermine whether encapsulation is applied (JS19080).

When the EF is enabled, the transmitter performs encapsulation on theupper layer packet (JS19090). When the EF is disabled, the transmitterdoes not perform separate processing on the corresponding packet stream.The transmitter transmits the packet stream (link layer packet) on whichprocessing is completed in the link layer, to a physical layer(JS19070). Header compression, encapsulation, and/or generation of linklayer may be performed by a link layer packet generator (i.e. link layerprocessor) in the transmitter.

The transmitter may generate service signaling channel (SCC) data. Theservice signaling channel data may be generated by a service signalingdata encoder. The service signaling data encoder may be included in alink layer processor and may present separately from the link layerprocessor. The service signaling channel data may include theaforementioned FIC and/or EAT. The service signaling channel data may betransmitted to the aforementioned dedicated channel.

FIG. 93 is a diagram illustrating an operation of a receiver forprocessing a broadcast signal according to an operation mode accordingto an embodiment of the present invention.

A receiver may receive information associated with an operation mode ina link layer together with a packet stream.

The receiver receives signaling information and/or channel information(JS20010). Here, a description of the signaling information and/or thechannel information is replaced with the above description.

The receiver selects a DP for receiving and processing according to thesignaling information and/or the channel information (JS20020).

The receiver performs decoding of a physical layer on the selected DPand receives a packet stream of a link layer (JS20030).

The receiver checks whether link layer mode control related signaling isincluded in the received signaling (JS20040).

When the receiver receives the link layer mode related information, thereceiver checks an EF (JS20050).

When the EF is enabled, the receiver performs a decapsulation process ona link layer packet (JS20060).

The receiver checks an HCF after decapsulation of the packet, andperforms a header decompression process when the HCF is enabled(JS20080).

The receiver transmits the packet on which header decompression isperformed, to an upper layer (e.g., an IP layer) (JS20090). During theaforementioned process, when the HCF and the EF are disabled, thereceiver recognizes the processed packet stream as an IP packet andtransmits the corresponding packet to the IP layer.

When the receiver does not receive link layer mode related informationor a corresponding system does not transmit the link layer mode relatedinformation to the receiver, the following operation is performed.

The receiver receives signaling information and/or channel information(JS20010) and selects a DP for reception and processing according tocorresponding information (JS20020). The receiver performs decoding ofthe physical layer on the selected DP to acquire a packet stream(JS20030).

The receiver checks whether the received signaling includes link layermode control related signaling (JS20040).

Since the receiver does not receive link layer mode related signaling,the receiver checks a format of the packet transmitted using physicallayer signaling, etc. (JS20100). Here, the physical layer signalinginformation may include information for identification of a type of thepacket included in a payload of the DP. When the packet transmitted fromthe physical layer is an IP packet, the receiver transmits the packet tothe IP layer without a separate process in a link layer.

When a packet transmitted from a physical layer is a packet on whichencapsulation is performed, the receiver performs a decapsulationprocess on the corresponding packet (JS20110).

The receiver checks the form of a packet included in a payload usinginformation such as a header, etc. of the link layer packet during thedecapsulation process (JS20120), and the receiver transmits thecorresponding packet to the IP layer processor when the payload is an IPpacket.

When the payload of the link layer packet is a compressed IP, thereceiver performs a decompression process on the corresponding packet(JS20130).

The receiver transmits the IP packet to an IP layer processor (JS20140).

FIG. 94 is a diagram illustrating information for identifying anencapsulation mode according to an embodiment of the present invention.

In a broadcast system, when processing in a link layer operates in oneor more modes, a procedure for determining as which mode processing inthe link layer operates (in a transmitter and/or a receiver) may beneeded. In a procedure of establishing a transmission link between thetransmitter and the receiver, the transmitter and/or the receiver mayconfirm configuration information of the link layer. This case maycorrespond to the case in which the receiver is initially set up orperforms a scan procedure for a service or a mobile receiver newlyenters an area within a transmission radius of the transmitter. Thisprocedure may be referred to as an initialization procedure or abootstrapping procedure. This procedure may be configured as a partialprocess of a procedure supported by the system without being configuredby an additional procedure. In this specification, this procedure willbe referred to as an initialization procedure.

Parameters needed in the initialization procedure may be determinedaccording to functions supported by a corresponding link layer and typesof operating modes possessed by each function. A description will begiven hereinafter of the parameters capable of determining functionsconstituting the link layer and operation modes according to thefunctions.

The above-described drawing illustrates parameters for identifying anencapsulation mode.

When a procedure for encapsulating a packet in a link layer or a upperlayer (e.g., an IP layer) can be configured, indexes are assigned torespective encapsulation modes and a proper field value may be allocatedto each index. The drawing illustrates an embodiment of a field valuemapped to each encapsulation mode. While it is assumed that a 2-bitfield value is assigned in this embodiment, the field value may beexpanded within a range permitted by the system in actualimplementation, when more supportable encapsulation modes are present.

In this embodiment, if a field of information indicating anencapsulation mode is set to ‘00’, the corresponding information mayrepresent that encapsulation in a link layer is bypasses and notperformed. If a field of information indicating an encapsulation mode isset to ‘01’, the corresponding information may represent that data isprocessed by a first encapsulation scheme in the link layer. If a fieldof information indicating an encapsulation mode is set to ‘10’, thecorresponding information may represent that data is processed by asecond encapsulation scheme in the link layer. If a field of informationindicating an encapsulation mode is set to ‘11’, the correspondinginformation may represent that data is processed by a thirdencapsulation scheme in the link layer.

FIG. 95 is a diagram illustrating information for identifying a headercompression mode according to an embodiment of the present invention.

Processing in a link layer may include a function of header compressionof an IP packet. If a few IP header compression schemes are capable ofbeing supported in the link layer, a transmitter may determine whichscheme the transmitter is to use.

Determination of a header compression mode generally accompanies anencapsulation function. Therefore, when the encapsulation mode isdisabled, the header compression mode may also be disabled. Theabove-described drawing illustrates an embodiment of a field valuemapped to each header compression mode. While it is assumed that a 3-bitfield value is assigned in this embodiment, the field value may beexpanded or shortened within a range permitted by the system in actualimplementation according to a supportable header compression mode.

In this embodiment, if a field of information indicating the headercompression mode is set to ‘000’, the corresponding information mayindicate that header compression processing for data is not performed ina link layer. If a field of information indicating the headercompression mode is set to ‘001’, the corresponding information mayindicate that header compression processing for data in the link layeruses an RoHC scheme. If a field of information indicating the headercompression mode is set to ‘010’, the corresponding information mayindicate that header compression processing for data in the link layeruses a second RoHC scheme. If a field of information indicating theheader compression mode is set to ‘011’, the corresponding informationmay indicate that header compression processing for data in the linklayer uses a third RoHC scheme. If a field of information indicating theheader compression mode is set to ‘100’ to ‘111’, the correspondinginformation may indicate that header compressing for data is reserved asa region for identifying a new header compression processing scheme fordata in the link layer.

FIG. 96 is a diagram illustrating information for identifying a packetreconfiguration mode according to an embodiment of the presentinvention.

To apply a header compression scheme to a unidirectional link such as abroadcast system, the broadcast system (transmitter and/or receiver)needs to rapidly acquire context information. The broadcast system maytransmit/receive a packet stream after a header compression procedure inan out-of-band form through reconfiguration of partial compressedpackets and/or extraction of context information. In the presentinvention, a mode for reconfiguring a packet or performing processingsuch as addition of information capable of identifying the structure ofthe packet may be referred to as a packet reconfiguration mode.

The packet reconfiguration mode may use a few schemes and the broadcastsystem may designate a corresponding scheme in an initializationprocedure of a link layer. The above-described drawing illustrates anembodiment of an index and a field value mapped to the packetreconfiguration mode. While it is assumed that a 2-bit field value isassigned in this embodiment, the field value may be expanded orshortened within a range permitted by the system in actualimplementation according to a supportable packet reconfiguration mode.

In this embodiment, if a field of information indicating the packetreconfiguration mode is set to ‘00’, corresponding information mayrepresent that reconfiguration for a packet transmitting data is notperformed in a link layer. If a field of information indicating thepacket reconfiguration mode is set to ‘01’, corresponding informationmay represent that a first reconfiguration scheme is performed for apacket transmitting data in the link layer. If a field of informationindicating the packet reconfiguration mode is set to ‘10’, correspondinginformation may represent that a second reconfiguration scheme isperformed for a packet transmitting data in the link layer. If a fieldof information indicating the packet reconfiguration mode is set to‘11’, corresponding information may represent that a thirdreconfiguration scheme is performed for a packet transmitting data inthe link layer.

FIG. 97 is a diagram illustrating a context transmission mode accordingto an embodiment of the present invention.

A transmission scheme of the above-described context information mayinclude one or more transmission modes. That is, the broadcast systemmay transmit the context information in many ways. In the broadcastsystem, a context transmission mode may be determined according to thesystem and/or a transmission path of a logical physical layer andinformation for identifying the context transmission scheme may besignaled. The above-described drawing illustrates an embodiment of anindex and a field value mapped to the context transmission mode. Whileit is assumed that a 3-bit field value is assigned in this embodiment,the field value may be expanded or shortened within a range permitted bythe system in actual implementation according to a supportable contexttransmission mode.

In this embodiment, if a field of information indicating the contexttransmission mode is set to ‘000’, corresponding field information mayrepresent that context information is transmitted as a firsttransmission mode. If a field of information indicating the contexttransmission mode is set to ‘001’, corresponding information mayrepresent that context information is transmitted as a secondtransmission mode. If a field of information indicating the contexttransmission mode is set to ‘010’, corresponding information mayrepresent that context information is transmitted as a thirdtransmission mode. If a field of information indicating the contexttransmission mode is set to ‘011’, corresponding information mayrepresent that context information is transmitted as a fourthtransmission mode. If a field of information indicating the contexttransmission mode is set to ‘100’, corresponding information mayrepresent that context information is transmitted as a fifthtransmission mode. If a field of information indicating a contexttransmission mode is set to ‘101’ to ‘111’, corresponding informationmay represent that context information is reserved to identify a newtransmission mode.

FIG. 98 is a diagram illustrating initialization information when RoHCis applied by a header compression scheme according to an embodiment ofthe present invention.

While the case in which RoHC is used for header compression has beendescribed by way of example in the present invention, similarinitialization information may be used in the broadcast system even whena header compression scheme of other types is used.

In the broadcast system, transmission of initialization informationsuitable for a corresponding compression scheme according to a headercompression mode may be needed. In this embodiment, an initializationparameter for the case in which a header compression mode is set to RoHCis described. Initialization information for RoHC may be used totransmit information about configuration of an RoHC channel which is alink between a compressor and a decompressor.

One RoHC channel may include one or more context information andinformation commonly applied to all contexts in the RoHC channel may betransmitted/received by being included in the initializationinformation. A path through which related information is transmitted byapplying RoHC may be referred to as an RoHC channel and, generally, theRoHC channel may be mapped to a link. In addition, the RoHC channel maybe generally transmitted through one DP and, in this case, the RoHCchannel may be expressed using information related to the DP.

The initialization information may include link_id information, max_cidinformation, large_cids information, num_profiles information, profiles() information, num_IP_stream information, and/or IP_address( )information.

link_id information represents an ID of a link (RoHC channel) to whichcorresponding information is applied. When the link or the RoHC channelis transmitted through one DP, link_id information may be replaced withDP_id.

max_cid information represents a maximum value of a CID. max_cidinformation may be used to inform a decompressor of the maximum value ofthe CID.

large_cids information has a Boolean value and identifies whether ashort CID (0 to 15) is used or an embedded CID (0 to 16383) is used inconfiguring a CID. Therefore, a byte size expressing the CID may also bedetermined.

num_profiles information represents the number of profiles supported inan identified RoHC channel.

profiles( ) information represents a range of a protocolheader-compressed in RoHC. Since a compressor and a decompressor shouldhave the same profile in RoHC to compress and recover a stream, areceiver may acquire a parameter of RoHC used in a transmitter fromprofiles( ) information.

num_IP_stream information represents the number of IP streamstransmitted through a channel (e.g., an RoHC channel).

IP_address information represents an address of an IP stream. IP_addressinformation may represent a destination address of a filtered IP streamwhich is input to an RoHC compressor (transmitter).

FIG. 99 is a diagram illustrating information for identifying link layersignaling path configuration according to an embodiment of the presentinvention.

In the broadcast system, generally, a path through which signalinginformation is delivered is designed not to be changed. However, whenthe system is changed or while replacement between different standardsoccurs, information about configuration of a physical layer in whichlink layer signaling information rather than an IP packet is transmittedneeds to be signaled. In addition, when a mobile receiver moves betweenregions covered by transmitters having different configurations, sincepaths through which link layer signaling information is transmitted maydiffer, the case in which link layer signaling path information shouldbe transmitted may occur. The above-described drawing illustratesinformation for identifying a signaling path which is a path throughwhich the link layer signaling information is transmitted/received.Indexes may be expanded or shortened with respect to the link layersignaling information according to a signaling transmission pathconfigured in a physical layer. Separately from configuration in a linklayer, operation of a corresponding channel may conform to a procedureof the physical layer.

The above-described drawing illustrates an embodiment in whichinformation about signaling path configuration is allocated to a fieldvalue. In this specification, when multiple signaling paths aresupported, indexes may be mapped to signaling paths having greatimportance in order of small values. Signaling paths having priorityprioritized according to an index value may also be identified.

Alternatively, the broadcast system may use all signaling paths havinghigher priority than signaling paths indicated by the information aboutsignaling path configuration. For example, when a signaling pathconfiguration index value is 3, a corresponding field value may be ‘011’indicating that all of a dedicated data path, a specific signalingchannel (FIC), and a specific signaling channel (EAC), priorities ofwhich are 1, 2, and 3, are being used.

Signaling of the above scheme can reduce the amount of data thattransmits signaling information.

FIG. 100 is a diagram illustrating information about signaling pathconfiguration by a bit mapping scheme according to an embodiment of thepresent invention.

The above-described information about signaling path configuration maybe transmitted/received through definition of a bit mapping scheme. Inthis embodiment, allocation of 4 bits to the information about signalingpath configuration is considered and signaling paths corresponding torespective bits b1, b2, b3, and b4 may be mapped. If a bit value of eachposition is 0, this may indicate that a corresponding path is disabledand, if a bit value of each position is 1, this may indicate that acorresponding path is enabled. For example, if a 4-bit signaling pathconfiguration field value is ‘1100’, this may indicate that thebroadcast system is using a dedicated DP and a specific signalingchannel (FIC) in a link layer.

FIG. 101 is a flowchart illustrating a link layer initializationprocedure according to an embodiment of the present invention.

If a receiver is powered on or a mobile receiver enters a transmissionregion of a new transmitter, the receiver may perform an initializationprocedure for all or some system configurations. In this case, aninitialization procedure for a link layer may also be performed. Initialsetup of the link layer in the receiver, using the above-describedinitialization parameters may be performed as illustrated in thedrawing.

The receiver enters an initialization procedure of a link layer(JS32010).

Upon entering the initialization procedure of the link layer, thereceiver selects an encapsulation mode (JS32020). The receiver mayselect the encapsulation mode using the above-described initializationparameters in this procedure.

The receiver determines whether encapsulation is enabled (JS32030). Thereceiver may determine whether encapsulation is enabled using theabove-described initialization parameters in this procedure.

Generally, since a header compression scheme is applied after theencapsulation procedure, if an encapsulation mode is disabled, thereceiver may determine that a header compression mode is disabled(JS32080). In this case, since it is not necessary for the receiver toproceed to the initialization procedure any more, the receiver mayimmediately transmit data to another layer or transition to a dataprocessing procedure.

The receiver selects a header compression mode (JS32040) when theencapsulation mode is enabled. Upon selecting the header compressionmode, the receiver may determine a header compression scheme applied toa packet, using the above-described initialization parameter.

The receiver determines whether header compression is enabled (JS32050).If header compression is disabled, the receiver may immediately transmitdata or transition to a data processing procedure.

If header compression is enabled, the receiver selects a packet streamreconfiguration mode and/or a context transmission mode (JS32060 andJS32070) with respect to a corresponding header compression scheme. Thereceiver may select respective modes using the above-describedinformation in this procedure.

Next, the receiver may transmit data for another processing procedure orperform the data processing procedure.

FIG. 102 is a flowchart illustrating a link layer initializationprocedure according to another embodiment of the present invention.

The receiver enters an initialization procedure of a link layer(JS33010).

The receiver identifies link layer signaling path configuration(JS33020). The receiver may identify a path through which link layersignaling information is transmitted, using the above-describedinformation.

The receiver selects an encapsulation mode (JS33030). The receiver mayselect the encapsulation mode using the above-described initializationparameter.

The receiver determines whether encapsulation is enabled (JS33040). Thereceiver may determine whether encapsulation is enabled, using theabove-described initialization parameter in this procedure.

Generally, since a header compression scheme is applied after theencapsulation procedure, if an encapsulation mode is disabled, thereceiver may determine that a header compression mode is disabled(JS34100). In this case, since it is not necessary for the receiver toproceed to the initialization procedure any more, the receiver mayimmediately transmit data to another layer or transition to a dataprocessing procedure.

The receiver selects a header compression mode (JS33050) when theencapsulation mode is enabled. Upon selecting the header compressionmode, the receiver may determine a header compression scheme applied toa packet, using the above-described initialization parameter.

The receiver determines whether header compression is enabled (JS33060).If header compression is disabled, the receiver may immediately transmitdata or transition to the data processing procedure.

If header compression is enabled, the receiver selects a packet streamreconfiguration mode and/or a context transmission mode (JS33070 andJS32080) with respect to a corresponding header compression scheme. Thereceiver may select respective modes using the above-describedinformation in this procedure.

The receiver performs header compression initialization (JS33090). Thereceiver may use the above-described information in a procedure ofperforming header compression initialization. Next, the receiver maytransmit data for another processing procedure or perform the dataprocessing procedure.

FIG. 103 is a diagram illustrating a signaling format for transmittingan initialization parameter according to an embodiment of the presentinvention.

To actually transmit the above-described initialization parameter to areceiver, the broadcast system may transmit/receive correspondinginformation in the form of a descriptor. When multiple links operated ina link layer configured in the system are present, link_id informationcapable of identifying the respective links may be assigned anddifferent parameters may be applied according to link_id information.For example, if a type of data transmitted to the link layer is an IPstream, when an IP address is not changed in the corresponding IPstream, configuration information may designate n IP address transmittedby a upper layer.

The link layer initialization descriptor for transmitting theinitialization parameter according to an embodiment of the presentinvention may include descriptor_tag information, descriptor_lengthinformation, num_link information, link_id information,encapsulation_mode information, header_compression_mode information,packet_reconfiguration_mode information, context_transmission_modeinformation, max_cid information, large_cids information, num_profilesinformation, and/or profiles( ) information. A description of the aboveinformation is replaced with a description of the above-describedinformation having a similar or identical name.

FIG. 104 is a diagram illustrating a signaling format for transmittingan initialization parameter according to another embodiment of thepresent invention.

The drawing illustrates a descriptor of another form to actuallytransmit the above-described initialization parameter to a receiver. Inthis embodiment, the above-described initial configuration informationof header compression is excluded. When an additional header compressioninitialization procedure is performed in data processing of each linklayer or an additional header compression parameter is given to a packetof each link layer, the descriptor configured in the same form as inthis embodiment may be transmitted and received.

The link layer initialization descriptor for transmitting theinitialization parameter according to another embodiment of the presentinvention may include descriptor_tag information, descriptor_lengthinformation, num_link information, link_id information,encapsulation_mode information, header_compression_mode information,packet_reconfiguration_mode information, and/orcontext_transmission_mode information. A description of the aboveinformation is replaced with a description of the above-describedinformation having a similar or identical name.

FIG. 105 is a diagram illustrating a signaling format for transmittingan initialization parameter according to another embodiment of thepresent invention.

The drawing illustrates a descriptor of another form to actuallytransmit the above-described initialization parameter to a receiver. Inthis embodiment, a descriptor for transmitting the initializationparameter includes configuration information about a signalingtransmission path without including initial configuration information ofheader compression.

The configuration parameter about the signaling transmission path mayuse a 4-bit mapping scheme as described above. When a broadcast system(or transmitter or a receiver) for processing a broadcast signal ischanged, a link layer signaling transmission scheme or the contents oflink layer signaling may differ. In this case, if the initializationparameter is transmitted in the same form as in this embodiment, theinitialization parameter may be used even in the case of change of linklayer signaling.

The link layer initialization descriptor for transmitting theinitialization parameter according to another embodiment of the presentinvention may include descriptor_tag information, descriptor_lengthinformation, num link information, signaling_path_configurationinformation, dedicated_DP_id information, link id information,encapsulation_mode information, header_compression_mode information,packet_reconfiguration_mode information, and/orcontext_transmission_mode information.

When the link layer signaling information is transmitted through adedicated DP, dedicated_DP_id information is information identifying thecorresponding DP. When the dedicated DP is determined as a path fortransmitting the signaling information in signaling path configuration,DP_id may be designated to include DP_id information in the descriptorfor transmitting the initialization parameter.

A description of the above information contained in the descriptor isreplaced with a description of the above-described information having asimilar or identical name.

FIG. 106 is a diagram illustrating a receiver according to an embodimentof the present invention.

The receiver according to an embodiment of the present invention mayinclude a tuner JS21010, an ADC JS21020, a demodulator JS21030, achannel synchronizer & equalizer JS21040, a channel decoder JS21050, anLI signaling parser JS21060, a signaling controller JS21070, a basebandcontroller JS21080, a link layer interface JS21090, an L2 signalingparser JS21100, packet header recovery JS21110, an IP packet filterJS21120, a common protocol stack processor JS21130, an SSC processingbuffer and parser JS21140, a service map database (DB) JS21150, aservice guide (SG) processor JS21160, a SG DB JS21170, an AV servicecontroller JS21180, a demultiplexer JS21190, a video decoder JS21200, avideo renderer J521210, an audio decoder JS21220, an audio rendererJS21230, a network switch JS21240, an IP packet filter JS21250, a TCP/IPstack processor JS21260, a data service controller JS21270, and/or asystem processor JS21280.

The tuner JS21010 receives a broadcast signal.

When a broadcast signal is an analog signal, the ADC JS21020 convertsthe broadcast signal to a digital signal.

The demodulator JS21030 demodulates the broadcast signal.

The channel synchronizer & equalizer JS21040 performs channelsynchronization and/or equalization.

The channel decoder JS21050 decodes a channel in the broadcast signal.

The L1 signaling parser JS21060 parses L1 signaling information from thebroadcast signal. The L1 signaling information may correspond tophysical layer signaling information. The L1 signaling information mayinclude a transmission parameter.

The signaling controller JS21070 processes the signaling information orthe broadcast receiver transmits the signaling information to anapparatus that requires the corresponding signaling information.

The baseband controller JS21080 controls processing of the broadcastsignal in a baseband. The baseband controller JS21080 may performprocessing in the physical layer on the broadcast signal using the L1signaling information. When a connection relation between the basebandcontroller J521080 and other apparatuses is not indicated, the basebandcontroller JS21080 may transmit the processed broadcast signal orbroadcast data to another apparatus in the receiver.

The link layer interface JS21090 accesses the link layer packet andacquires the link layer packet.

The L2 signaling parser JS21100 parses L2 signaling information. The L2signaling information may correspond to information included in theaforementioned link layer signaling packet.

When header compression is applied to a packet of a upper layer (e.g.,an IP packet) than a link layer, the packet header recovery JS21110performs header decompression on the packet. Here, the packet headerrecovery JS21110 may restore a header of the packet of the upper layerusing information for identification of whether the aforementionedheader compression is applied.

The IP packet filter JS21120 filters the IP packet transmitted to aspecific IP address and/or UDP number. The IP packet transmitted to thespecific IP address and/or UDP number may include signaling informationtransmitted through the aforementioned dedicated channel. The IP packettransmitted to the specific IP address and/or UDP number may include theaforementioned FIC, FIT, EAT, and/or emergency alert message (EAM).

The common protocol stack processor JS21130 processes data according toa protocol of each layer. For example, the common protocol stackprocessor JS21130 decodes or parses the corresponding IP packetaccording to a protocol of an IP layer and/or a upper layer than the IPlayer.

The SSC processing buffer and parser JS21140 stores or parses signalinginformation transmitted to a service signaling channel (SSC). Thespecific IP packet may be designated as an SSC and the SSC may includeinformation for acquisition of a service, attribute information includedin the service, DVB-SI information, and/or PSI/PSIP information.

The service map DB JS21150 stores a service map table. The service maptable includes attribute information about a broadcast service. Theservice map table may be included in the SSC and transmitted.

The SG processor JS21160 parses or decodes a service guide.

The SG DB JS21170 stores the service guide.

The AV service controller JS21180 performs overall control foracquisition of broadcast AV data.

The demultiplexer JS21190 divides broadcast data into video data andaudio data.

The video decoder JS21200 decodes video data.

The video renderer JS21210 generates video provided to a user using thedecoded video data.

The audio decoder JS21220 decodes audio data.

The audio renderer JS21230 generates audio provided to the user usingthe decoded audio data.

The network switch JS21240 controls an interface with other networksexcept for a broadcast network. For example, the network switch JS21240may access an IP network and may directly receive an IP packet.

The IP packet filter JS21250 filters an IP packet having a specific IPaddress and/or a UDP number.

TCP/IP stack processor JS21260 decapsulates an IP packet according to aprotocol of TCP/IP.

The data service controller JS21270 controls processing of a dataservice.

The system processor JS21280 performs overall control on the receiver.

FIG. 107 illustrates a header structure of a link layer packet accordingto another embodiment of the present invention.

The present embodiment may correspond to a header structure of a linklayer packet that encapsulates and includes transport stream (TS)packets when a TS packet is input to a link layer.

In this case, a header of the link layer packet may have a differentstructure from the aforementioned header structure of the link layerpacket. Needless to say, in some embodiments, when a TS packet isencapsulated, the header of the link layer packet may also have the samestructure as the aforementioned header structure of the link layerpacket.

In the illustrated embodiment t107010, a link layer packet header mayinclude a packet type field, a count field, an NPDI field, and/or a HCIfield. In some embodiments, the link layer packet header may furtherinclude a reserved bit R for future use.

The packet type field may correspond to the aforementioned Packet Typefield. As described above, the packet type field may indicate a type ofan input packet included in a payload of the corresponding link layerpacket. This case corresponds to the case in which the TS packet isencapsulated, and thus the packet type field may indicate that the TSpacket is encapsulated. As described above, the packet type field mayindicate whether IPv4 IP packet, a compressed IP packet, L2 signaling,etc. are included in the link layer payload according to a value of thepacket type field.

The count field may indicate the number of TS packets included in apayload of the corresponding link layer packet. This field may besubsequent to the packet type field and in some embodiments, may also bereferred to as a NUM TS field. The count field may have a value of 5bits as illustrated in the drawing or in some embodiments, may have avalue of 4 bits.

A region including the packet type field and/or the count field may bereferred to as a base header of a TS packet encapsulation case. When thecount field has a value of 4 bits, the remaining 1 bit of the baseheader may correspond to flag information indicating whether anadditional header including an additional field is present after thebase header.

The additional header of the TS packet encapsulation case may bepositioned after the base header. The aforementioned NPDI field and/orHCI field may be included in the additional header. The NPDI field andthe HCI field may be referred to as a deleted null packet (DNP) fieldand a header deletion mode (HDM) field, respectively.

The NPDI field may indicate the number of deleted null packets that havebeen positioned prior to TS packets included in the corresponding linklayer packet. Prior to TS packet encapsulation, an overhead reductionprocess may be performed on input packets. In a null packet deletionprocess as one of overhead reduction process, null packets of the inputstream may be deleted. The NPDI field may indicate the deleted nullpackets such that a receiving side can recover null packets. The NPDIfield may function as an indicator (flag) indicating whether a nullpacket deletion process is performed according to a value of the NPDIfield. When the NPDI field indicates that there is no deleted nullpacket, the NPDI field may also indicate that null packet deletion hasnot been performed. The overhead reduction process will be describedlater.

In some embodiments, when the HCI field to be described later has avalue of 0 and the NPDI field has a value of 0, null packets may bedeleted by as much as the number of maximum null packets indicated bythe NPDI field. For example, when the NPDI field has 7 bits, this mayindicate that a total of 128 null packets are deleted. When the HCIfield to be described later has a value of 1 and the NPDI field has avalue of 0, any null packet may not be deleted. In general, null packetsmay be deleted by as much as the value of the NPDI. That is, when thevalue of the NPDI is 5, this may indicate that 5 null packet has beendeleted.

The HCI field may indicate whether a header deletion process has beenperformed on the corresponding link layer packet. The header deletionprocess may be included in the aforementioned overhead reductionprocess. In some embodiments, the HCI field may have a size of 1 bit or2 bits. The HCI field of 1 bit may indicate whether the header deletionprocess is performed as described above. When the HCI field has a sizeof 2 bits, the HCI field may indicate a type of a header deletion methodthat has been performed to delete a header as well as whether the headerdeletion process. The type of the header deletion method will bedescribed later.

The illustrated embodiment t107020 may be formed by illustrating theaforementioned header structure embodiment t107010 in detail. DNPconfiguration information may be further subsequent according to a valueof the aforementioned NPDI field. When the NPDI field indicates thatthere is no deleted null packet (e.g., when a value of the NPDI field is0x00), the DNP configuration information may not be subsequent. When theNPDI field indicates that deleted null packets are present and indicatesthe number of the deleted null packets, the DNP configurationinformation may be present.

The DNP configuration information may indicate information about thedeleted null packets. The DNP configuration information may include oneor more fields. The fields may include fields indicating informationabout an original position of the deleted null packet, information aboutthe number of the deleted null packets, etc. in the corresponding linklayer packet.

In some embodiments, the DNP configuration information may not bepresent according to a method for deleting a null packet even when thedeleted null packet is present.

FIG. 108 illustrates a header structure of a link layer packet accordingto another embodiment of the present invention.

The present embodiment may also correspond to a header structure of alink layer packet when a TS packet is input to a link layer.

The header structure of the present embodiment t108010 may also includethe aforementioned packet type field, count field, NPDI field, and/orHCI field. These fields may perform the same functions as theaforementioned functions and may be just different in terms of a bitnumber, etc.

In the present embodiment, an optional field indicator (OP) field may beadded. The OP field may be a field indicating whether the aforementionedadditional header is present. The OP field may be present in a baseheader and may have a size of 1 bit. In this case, the count field mayhave a size of 4 bits. In some embodiments, the OP field may also bereferred to as an additional header flag (AHF) field. According to avalue of the OP field, the additional header may or may not be presentafter the base header. According to a value of the OP field, whether theNPDI field and/or the HCI field is present, and in this regard, when thenull packet deletion or header deletion process is not performed in theaforementioned overhead reduction process, the NPDI field and/or the HCIfield may not be present. That is, the OP field may indicate whether thenull packet deletion or header deletion process has been performed ondata of the corresponding link layer packet as well as may function as asimple flag indicating that whether the additional header is present.That is, when the null packet deletion or the header deletion isperformed, the OP field may have a value of 1 and the additional headermay also be present.

The illustrated embodiment t108020 may be formed by illustrating theaforementioned header structure embodiment t108010 in detail. Accordingto a value of the OP field of the base header, the additional header maynot be present (0, End of Header) or may be present (1). Then, like inthe aforementioned embodiment, according to a value of the NPDI, whetherDNP configuration information is present may be determined. Here, theDNP configuration may have different information according to a value ofa HCI field or a specific field to be added to a reserved bit.

FIG. 109 illustrates a header structure of a link layer packet accordingto another embodiment of the present invention.

The present embodiment may also correspond to a header structure of alink layer packet when a TS packet is input to a link layer.

The header structure of the present embodiment t109010 may also includethe aforementioned packet type field, count field, OP field, NPDI field,and/or HCI field. These fields may perform the same functions as theaforementioned functions and may be just different in terms of a bitnumber, etc.

In the present embodiment, I field may be further added. The I field maybe an ISSY indicator and indicate whether ISSY information is present inthe corresponding link layer packet. When a value of I is 0, the ISSYinformation may not be present in the corresponding link layer packetand link layer packet header. When a value of I is 1, ISSY informationmay be present in the corresponding link layer packet to link layerpacket header. Here, input stream synchronizer (ISSY) information may beinformation for synchronization of an input stream and may have clockreference information of an input stream related to a current link layerpacket. The ISSY may be used to know accurate timing an output streamwhile a receiver regenerates the output stream at a receiving side.

The illustrated embodiment t109020 may be formed by illustrating theaforementioned header structure embodiment t109010 in detail. Accordingto values of the aforementioned OP field and NPDI field, cases for theheader structure may be classified, which is the same as the abovedescription. According to a value of the aforementioned I field, ISSYinformation may or may not be present in the corresponding link layerpacket. When the I field is 0, the ISSY information may not be added,and when the I field is 1, the ISSY information may be present. The ISSYinformation may included in the illustrated ISSY field, and in someembodiments, a position of the ISSY field may be changed. The ISSYinformation may be positioned in a link layer payload, and in someembodiments, the ISSY information may be positioned in a BB packet, butnot in the link layer packet.

FIG. 110 illustrates a header structure of a link layer packet accordingto another embodiment of the present invention.

The present embodiment may also correspond to a header structure of alink layer packet when a TS packet is input to a link layer.

The header structure of the present embodiment may also include theaforementioned packet type field, NUMTS field, AHF field, HDM field,and/or DNP field. The NUMTS field may be another term of theaforementioned count field. The AHF field may be another term of theaforementioned OP field. The HDM field may be another term of theaforementioned HCI field. The DNP field may be another term of theaforementioned NPDI field. These fields may perform the same functionsas the aforementioned functions and may be just different in terms of abit number, etc.

In the present embodiment, a base header of the link layer packet mayinclude a packet type field, a NUMTS field, and/or an AHF field. Thepacket type field may indicate that the TS packet is included in apayload, the NUMTS field may indicate the number of TS packets includedin the payload, and the AHF field may indicate whether an additionalheader is present after the base header, a detailed description of whichis the same as the above description.

In addition, the additional header may include a HDM field and/or a DNPfield. In the present embodiment, these fields may have sizes of 1 bitand 7 bits, respectively. The HDM field may indicate whether theaforementioned header deletion process has been performed. The DNP fieldmay indicate whether the aforementioned null packet deletion has beenperformed and indicate the number of the deleted null packets when thenull packet deletion has been performed, a detailed description of whichis the same as the above description.

FIG. 111 is a diagram for explanation of an overhead reduction processwhen a TS packet is input to a link layer according to an embodiment ofthe present invention.

As described above, when an input packet is input to a link layer, anoverhead reduction process may be performed prior to encapsulation. Theoverhead reduction process may be performed to enhance transmissionefficiency. The overhead reduction may include at least one overheadreduction mechanism. The overhead reduction mechanism may be used for anIP packet, etc. but not for a TS packet.

One of examples of the overhead reduction mechanism may be a sync byteremoval mechanism. Sync byte and sync information may be positioned in afront portion of each TS packet. The sync byte may be information usedfor synchronization of an input packet.

However, the sync byte has a size of 1 byte, has a fixed value of 0x47,and is positioned in a first byte of the TS packet, and thus it may bedifficult to regenerate the sync byte at a receiving side. Accordingly,the sync byte may be deleted prior to transmission in order to enhancetransmission efficiency. In some embodiments, deletion of the sync bytemay always be performed.

The overhead reduction mechanism may also include a null packet deletionmechanism. In the case of an input stream, in particular, a TS inputstream, null packets for fixed transmission efficiency as well as a TSpacket may be included in the input stream. The null packets may be justoverhead in terms of transmission. The null packets may have a value ofPID 0x1FFF, and since the null packets may be recoverable at a receivingside, the information may be deleted prior to transmission. The nullpackets may be recovered according to information such as theaforementioned DNP field.

When the null packet deletion mechanism is applied, the aforementionedDNP field may be reset to 0. Then, null packets in the input stream maybe sequentially deleted. In this process, a value of the DNP field maybe increased by 1 as null packets are deleted. In this manner, a processfor reflection to the null packet deletion and the DNP value iscontinuously performed and then may be stopped when a first TS packet (apacket that is not a null packet) appears. A group consecutive usefulinput packets started from the first TS packet may be encapsulated in apayload of the link layer packet. Simultaneously, a value of the DNPfield of the corresponding link layer packet header may be determined asa value of the increased DNP. That is, the DNP field may indicate thenumber of null packets that have been deleted prior to the correspondinglink layer packet. Then, the DNP field may be reset to 0 for a next linklayer packet.

The overhead reduction mechanism may also include a header deletionmechanism. The mechanism may be a mechanism for deleting packet headershaving common information items among TS packets headers. For example,when two or more consecutive TS packets include common informationitems, respectively and only a value of a continuity counter field inthe TS packets is gradually increased, the header deletion mechanism maybe applied.

In this case, only a header of a first TS packet among the consecutiveTS packets may be transmitted and headers of the remaining TS packetsmay be deleted. A receiving side may recover headers of the deleted TSpackets using the aforementioned NUMTS field and HDM field. This isbecause, the deleted headers can have the same value as the first TSpacket header and the continuity counter field can be increased from avalue of the continuity counter field of the first TS packet header by 1so as to be recovered.

In some embodiments, the null packet deletion mechanism and the headerdeletion mechanism may be omitted, and when all mechanisms are used,sync byte deletion, null packet deletion, and header deletion mechanismsmay be performed in the stated order.

The illustrated embodiment may correspond to a structure of a link layerpacket when the null packet deletion and the header deletion mechanismare not performed. In the present embodiment, 7 input packets areencapsulated as the link layer packet.

The 7 input packets may be sequentially concatenated and may bepositioned in a payload of the link layer packet. The header accordingto the aforementioned embodiments may be positioned in a header portionof the link layer packet. In the illustrated embodiment, the headeraccording to two embodiments of the present invention among theaforementioned embodiments is included in the header portion. However,the link header structure according to the other aforementionedembodiments may be used.

In packet structure #1, the packet type field may have a value of 010.This is because TS packets are encapsulated. The count field and theNUMTS field may indicate that the 7 input packets are encapsulated. TheNPDI field and the HCI field may indicate that the null packet deletionand header deletion mechanisms are not performed, respectively.

In packet structure #2, the packet type field and the count field mayhave the same values as in packet structure #1. Here, a header structureof packet structure #2 may be a header structure having theaforementioned OP field. In the OP field and the AHF field, the nullpacket deletion and header deletion mechanisms are not performed, andthus the OP field and the AHF field may have a value of 0. Accordingly,the additional header may not be present, and fields for the null packetdeletion and header deletion mechanisms may not be present.

FIG. 112 is a diagram for explanation of a null packet deletion pointer(NPDP) field and a deleted null packet counter (DNPC) in an overheadreduction process of a TS packet according to another embodiment of thepresent invention.

The null packet deletion process has been described above. Unlike in theaforementioned embodiment of the null packet deletion mechanism, anembodiment of a null packet deletion mechanism in which a NPDP field isadded and used may also be present. The NPDP field may indicate aposition in which a null packet is deleted and provide informationrequired to recover a null packet at a receiving side. In the case of anull packet deletion mechanism without the aforementioned NPDP, duringthis process, deleted null packets may be positioned prior to a first TSpacket, and deleted null packets may not be positioned between TSpackets included in the link layer payload.

Null packets other than the TS packet may be present in an input stream.At a transmitting side, null packets may be deleted. Then, asillustrated, DNPC information may be inserted into positions of thedeleted null packets. The DNPC information may be a field indicating thenumber of deleted null packets in the corresponding position. In someembodiments, the field may have a size of 1 byte and accordingly, maycount 256 null packets.

In some embodiments, the DNPC information may be present together withTS packets in a payload of the link layer packet or positioned in aheader portion of the link layer packet. In any embodiment, positions inwhich null packets are deleted may be indicated by the NPDP field. Amethod for indicating a position of the deleted null packet by the NPDPfield will be described later. Later, a receiver may generate nullpackets and fill an original position with the null packets using theseinformation items.

FIG. 113 is a diagram for explanation of a NPDP field and a DNPC fieldin an overhead reduction process of a TS packet according to anotherembodiment of the present invention.

The aforementioned NPDP field may indicate positions in which nullpackets are deleted in an input stream. The NPDP field may be positionedin a header of the link layer packet. The NPDP field may include aplurality of pointing bits. The number of the pointing bits included inthe NPDP field may be equal to the number of TS packets included in thecorresponding link layer packets. For byte alignment, padding bits maybe added behind the pointing bit.

Each pointing bit of the NPDP field may indicate whether null packetsbehind the TS packet are deleted with respect to each encapsulated TSpacket. For example, a first pointing bit may be related to a first TSpacket included in a payload. The first pointing bit may indicatewhether null packets are present behind the first TS packet and deleted.When a value of the first pointing bit is 0, a null packet may not bepresent behind the first TS packet. When a value of the first pointingbit is 1, a null packet may be present behind the first TS packet anddeleted. In this case, the number of the deleted null packets may beindicated by the aforementioned DNPC information. As described above,the DNPC information may be positioned in a link layer header orpositioned in a position in which the deleted null packet is deleted.

In some embodiments, one of fields positioned in the TS packet headermay be re-used without separately configuring the NPDP field so as toachieve the same effect as the NPDP field. For example, a transporterror indicator (TEI) field positioned behind a sync byte 0x47) of eachTS packet may be used. This field may not be used when TS packets areconcatenated and encapsulated in a link layer packet. Accordingly, thisfield may be used to indicate whether null packets behind a current TSpacket are deleted. That is, this field may be used as a pointing bit.

FIG. 114 illustrates a structure of a link layer packet when a NPDPfield/DNPC field is used according to an embodiment of the presentinvention.

The illustrated embodiment may correspond to the case in which theaforementioned DNPC field is positioned at a position in which each nullpacket is positioned. In the illustrated embodiment, the link layerheader may be one of the link layer headers according to theaforementioned embodiments of the present invention. However,embodiments of the present invention are not limited thereto, and thelink layer header according to one of the aforementioned embodiments ofthe present invention may be used.

The aforementioned NPDP field may be positioned behind the link layerheader. The NPDP field may be included in an additional header of thelink layer header, and in some embodiments, may be included in anoptional header positioned behind the additional header. In someembodiments, the NPDP field may be included in one of the DNPconfiguration information of the aforementioned additional header.

As described above, the NPDP field may indicate whether a null packetbehind each TS packet is deleted with respect to each TS packet. In thepresent embodiment, the NPDP field is illustrated as 1 byte, but asdescribed above, the size of the NPDP field may be changed according tothe number of pointing bits.

The DNPC field included in each deleted position may indicate the numberof null packets that have been originally present in a correspondingposition.

Here, both the DNPC field and the NPDP field may be included in theaforementioned DNP configuration information.

FIG. 115 is a diagram of a structure of a link layer packet when a NPDPfield/DNPC field is used according to another embodiment of the presentinvention.

The illustrated embodiment may correspond to a case in which theaforementioned DNPC field is included in behind a link layer header, butnot in at a position in which each null packet is deleted.

In this case, the respective DNPC fields may be positioned in an orderof the deleted null packet indicated by the respective DNPC fields.Here, the DNPC fields may be sequentially positioned behind the NPDPfield.

The DNPC field may be included in an additional header of the link layerheader, and in some embodiments, may be included an optional headerpositioned behind the additional header. In some embodiments, the DNPCfield may be included in one of the DNP configuration information of theaforementioned additional header.

Also in the present embodiment, the NPDP field may indicate whether nullpackets behind each TS packet are deleted and indicate the number ofnull packets that have been present in positions in which the DNPCfields are deleted in the order.

In the illustrated embodiment, DNPC fields may be sequentiallypositioned and indicate the number of null packets that have beenpresent in the respective deleted positions, but in some embodiments,the order of the DNPC fields may be changed. In this case, additionalinformation indicating a deleted position matched to the numberindicated by each DNPC field may be further included in the link layerheader.

FIG. 116 illustrates a null packet deletion mechanism according to aNPDP field/DNPC field according to an embodiment of the presentinvention.

The illustrated embodiment may correspond to an example of a null packetdeletion mechanism using the aforementioned NPDP/DNPC field. Here, thelink layer header may use one of the aforementioned embodiments of thelink layer header. However, embodiments of the present invention are notlimited thereto, and the link layer header according to one of theaforementioned embodiments of the present invention may be used.

There is no null packet behind the first illustrated TS packet. However,two null packets may be present behind a second TS packet. The two nullpackets may be deleted and a DNPC #1 field may be instead positioned inthe corresponding position. The DNPC #1 field may have a valueindicating that two null packets are deleted.

Then, there is no null packet behind third and fourth TS packets and nnull packets may be pre sent behind a fifth TS packet. The null packetsmay also be deleted and a DNPC #2 field may be instead positioned in thecorresponding position. The DNPC #2 field may have a value indicatingthat the n null packets are deleted.

In this manner, since one null packet is present behind a 7^(th) TSpacket, the null packet may be deleted, and a DNPC #3 field having avalue indicating that one null packet is deleted may be positioned.

In this manner, after the overhead reduction process is performed (here,it is assumed that a sync byte deletion mechanism is already performedand a header deletion mechanism is not performed), the input packets maybe encapsulated. When the encapsulation is performed, a link layerpayload may be configured and a link layer header may be added in frontof the link layer payload.

When DNPC fields are positioned in respective null packet deletionpotions, the DNPC fields may be positioned between TS packets. Asdescribed above, the NPDP field may indicate whether null packets behindthe respective TS packets are deleted using the pointing bits. Inreality, the number of the deleted packets may be known using values ofthe DNPC fields.

When the DNPC fields are collectively positioned behind the NPDP field,the plurality of DNPC fields is positioned behind the NPDP field and aplurality of TS packets may be sequentially positioned behind the DNPCfields, as illustrated.

Here, the NPDP has a plurality of pointing bits, the number of which maybe determined according to a value of the NUMTS field of a header. Inthis case, 10 TS packets are encapsulated, and thus the NUMTS field mayindicate that 10 input packets are encapsulated. Accordingly, the NPDPmay have 10 pointing bits. For byte alignment, padding of 6 bits may besubsequent.

Each of the 10 pointing bits may indicate whether there is a deletednull packet behind each TS packet. In the present embodiment, nullpackets are present behind second, fifth, and seventh TS packets, andthus second, fifth, and seventh pointing bits may have a value of 1. Theremaining pointing bits may have a value of 0. Since 2, n, and 1 nullpackets are present behind the second, fifth, and seventh TS packets,respectively, the DNPC fields may have values of 2, n, and 1,respectively.

The NPDI field may indicate the number of all of the deleted nullpackets with respect to a null packet deletion mechanism of the case inwhich the DNPC/NPDP field is not used. Accordingly, in this case, theNPDI field may have a value of 2+n+1. However, the NPDI field of thecase in which the NPC/NPDP field is used may be used to indicate thenumber of DNPC fields in the link layer packet. In this case, the NPDIfield may have a value of 3. This is because null packets have beendeleted in a total of three places.

FIG. 117 illustrates a null packet deletion mechanism according to aNPDP field/DNPC field according to another embodiment of the presentinvention.

The present embodiment may also be the same as the above description.Similarly, 2, n, and 1 null packets may be present behind second, fifth,and seventh TS packets, respectively. The null packets may be deletedand DNPC fields indicating the number of the deleted null packets may bepresent. In some embodiments, the DNPC fields may be present inpositions corresponding to the deleted null packets or may becollectively positioned behind the NPDP field. Pointing bits may also bethe same as the above description.

Unlike in the aforementioned embodiment, in the present embodiment, alink layer header including an OP field may be used. Unlike in the abovedescription, a different type of a link layer header may also be used.

FIG. 118 is a diagram illustrating a packet length indication method ofa link layer packet including a TS packet according to an embodiment ofthe present invention.

As described above, when the HCI field and the HDM field have a size of1 bit, the HCI field and the HDM field may indicate whether a headerdeletion process is performed. In this case, the header deletion processmay refer to a header deletion mechanism for deleting the aforementionedcommon header.

When the HCI field has a size of 2 bits, the HCI field may indicate atype of a performed header deletion process as well as whether theheader deletion process is performed. When the HCI field has a value of00, a separate header deletion mechanism may not be performed. In thiscase, only the aforementioned link byte deletion mechanism may beperformed with respect to an entire overhead reduction process. In thiscase, each TS packet header may have a size of 3 bytes. When the HCIfield has a value of 01, only a sync byte may be deleted with respect toa first TS packet, and headers may be reduced on 2 bytes basis withreference to information of a header of the first TS packet with respectto the remaining TS packet. When the HCI field has a value of 10, only async byte may be deleted with respect to the first TS packet, andheaders may be reduced on 1 byte basis with reference to information ofa header of the first TS packet with respect to the remaining TS packet.When the HCI field has a value of 11, the aforementioned headermechanism for deleting a common header may be applied.

A TS packet may have a fixed length. After the sync byte deletionmechanism is applied, sync byte also has 1 byte, and thus the TS packetafter the sync byte deletion mechanism is applied may also have a fixedlength. Accordingly, with respect to a link layer packet of a TS packet,a header thereof may not have a separate length field. An entire packetlength may be indicated simply using a packet number.

Here, assuming that the link layer header has a length of 2 bytes, avalue of the NUMTS field may be c and a value of the NPDI field may ben. In this case, it may be assumed that the NPDP field is used. Anoperator [ ] may refer to a smallest integer among integers greater thana corresponding value.

Case #1 may correspond to a case in which a separate NPDP field is used.In this case, as illustrated, according to a type of a header deletionmechanism indicated by the HCI field, a length of the link layer packetmay be indicated. Here, a length of the TS packet may be 188 bytes.

Case #2 may correspond to a case in which one of bits of a TS packetheader is used as a pointing bit. That is, without a separate NPDPfield, pointing bits may be present in each TS packet header. In thiscase, as illustrated, according to a type of a header deletion mechanismindicated by the HCI field, a length of a link layer packet may beindicated.

In each case, when ISSY information is included, the length of the linklayer packet may be increased by as much as the size of the ISSYinformation.

When the OP field is used, if the OP field indicates that an additionalheader is present, as described above. That is, in the case of OP=1, thelength of the link layer packet may be indicated in each case accordingto the shown mathematical expressions.

When OP=0, that is, when an additional header is not present, the lengthof the link layer packet may be 1+(187*c) bytes. When sync byte deletionis not applied, the length of the link layer packet may be 1+(188*c)bytes.

Similarly, when the OP field is used, if ISSY is included, the length ofthe link layer packet may also be increased by as much as the size ofthe ISSY information.

FIG. 119 is a diagram illustrating a header structure of a link layerpacket according to another embodiment of the present invention.

The present embodiment may correspond to a link layer header structureobtained by adding an M field to the aforementioned link layer packetstructure. A packet type field, a count field, an OP field, an HCIfield, an NPDI field, and/or DNP configuration information may be thesame as the above description.

As described above, whether the additional header is present may bedetermined according to a value of the OP field. When the additionalheader is present, a first bit of the additional header may be allocatedto the M field. The M field may determine a mode of the additionalheader.

When a value of the M field is 0, a basic null packet deletion mechanismmay be applied. In this case, the DNP count field may be positioned inthe remaining additional header. The DNP count field may correspond to aDNP field in the case of a null packet deletion mechanism in which theaforementioned NPDP/DNPC is not used. Here, in some embodiments, the Mfield may be substituted with a HDM field (1 byte). The M field issubstituted with the HDM field when a corresponding system is designedas a system in which only the basic null packet deletion mechanism (inwhich the NPDP/DNPC is not used) is used.

When the M field has a value of 1, a null packet deletion mechanismusing the NPDP/DNPC may be applied or one of various header deletionprocesses may be applied. In this case, the aforementioned HCI field,NPDI field, etc. may be positioned. According to a value of the NPDIfield, DNP configuration information may be further added. The DNPconfiguration information may include the aforementioned NPDP/DNPCinformation. Here, the HCI field may be a HCI field of 2 bits.

The illustrated first embodiment (Simple Encapsulation Mode) maycorrespond to a header structure to which a null packet deletion orheader deletion mechanism is not applied. The OP field and the AHF fieldmay have a value of 0 and this value may indicate that an additionalheader is not present and that a null packet deletion/header deletionmechanism is not applied.

The illustrated second embodiment (Basic Null Packet Deletion Mode) maycorrespond to a header structure to which the aforementioned basic nullpacket deletion mechanism is applied. The OP field may have a valueof 1. An M field may have a value of 0 and a DNP count field may bepositioned in the remaining additional header portion.

The illustrated third embodiment (Header Compression Mode) maycorrespond to a header structure to which one of various header deletionprocesses is applied. The OP field and the M field may have a valueof 1. The HCI field may indicate one type of the applied header deletionmechanisms. In this case, the HCI field may have 2 bits.

The illustrated fourth embodiment (Extended Null Packet Deletion Mode)may correspond to a header structure to which a null packet deletionmechanism using NPDP/DNPC is applied. The OP field and the M field mayhave a value of 1. The HCI field may have a value of 00 when a headerdeletion process is not applied. According to a value of the NPDI, theDNP configuration information may be added and NPDP/DNPC information maybe included in the DNP configuration information. In this case, the HCIfield may have 2 bits.

The illustrated fifth embodiment (Extended Null Packet Deletion withHeader Compression Mode) may correspond to a header structure to which anull packet deletion mechanism using NPDP/DNPC and one of various headerdeletion processes are applied. The OP field and the M field may have avalue of 1. The HCI field may indicate one type of the applied headerdeletion mechanisms. According to a value of the NPDI, DNP configurationinformation may be added and the NPDP/DNPC information may be includedin the DNP configuration information. In this case, the HCI field mayhave 2 bits.

FIG. 120 illustrates a header structure of a link layer packet accordingto another embodiment of the present invention.

The present embodiment may correspond to a link layer header structureobtained by adding an M field and/or a CE field to the aforementionedlink layer packet structure. A packet type field, a count field, an OPfield, an HCI field, an NPDI field, and/or DNP configuration informationmay be the same as the above description.

As described above, whether the additional header is present may bedetermined according to a value of the OP field, and according to the Mfield of the additional header, a mode of the additional header may bedetermined. A case in which the M field has 0 is the same as the abovedescription. When the M field has 1, the CE field may be further added.In this case, the HCI field may be an HCI field of 1 bit. Then,according to a value of the NPDI field, DNP configuration informationmay be further added. The DNP configuration information may include theaforementioned NPDP/DNPC information.

A count extension (CE) field may be extension of the aforementionedcount field and NUMTS field. That is, the CE field may be used to extendthe number of encapsulated TS packets. When TS packets, the number ofwhich is equal to or greater than the number of indicated by theaforementioned count field and NUMTS field are encapsulated, anadditional bit may be provided using the CE field. More TS packets maybe indicated using these bits. The CE field may be connectively usedwith the aforementioned count field and NUMTS

FIELD

The illustrated first to fifth embodiments have been described above.However, in this case, the HCI field may have a size of 1 bit instead of2 bits and the CE field may be allocated to the remaining bit, that is,1 bit.

FIG. 121 is a diagram illustrating a method for configuring a link layeron a protocol stack according to an embodiment of the present invention.

A broadcast system may be continuously evolved. The present inventionproposes a method for configuring a link layer on a protocol and amethod for embodying the link layer according to evolution of abroadcast system.

When the link layer is also changed during evolution of the broadcastsystem, backward compatibility needs to be considered. In addition, itneeds to be considered that the link layer is entirely changed.According to change in the broadcast system, a function of the linklayer may be added, deleted, or changed, and a configuration of the linklayer may also be changed. In this case, signaling may also be performedon the change, and thus there may be a need for an additional signalingmethod for the signaling to be performed on the change.

When various broadcast signals with different standards may coexist in anarrow area and a receiver acquires the broadcast signals, there may bea need to define the different standards. In addition, there may also bea need for signaling for the standards.

In a process for changing the system, an effective changing method mayalso be considered with respect to a method for the process. All systemsand layer configurations may be simultaneously changed but may besequentially changed from some systems as a starting pointing. In thiscase, during a system changing period, each standard needs to be definedfor differentiation between a past system and a current system, andsignaling for indicating configuration information for the standard maybe required.

The present invention describes the configuration and signaling for alink layer when the changing process is performed on the link layer.However, the present invention is not limited thereto, and in all casesin which system change is applied, methods proposed by the presentinvention may be applied to change of all layers and functionality oflayers.

The illustrated embodiment corresponds to a case in which a specificlayer (or a link layer) has one or more different standards. Forexample, a link layer may include one or more layers with differentstandards. In addition, initially, the link layer includes only a layerwith one standard but layers with different standards may be graduallyadded according to system change. Here, when one layer includes aplurality of different layers, each layer may also be referred to as asub layer. That is, in the illustrated embodiment, the link layer mayinclude sub layers link layer A, link layer B, . . . link layer Z.

The illustrated embodiment corresponds to a method for configuring abasic protocol. Link layers A to Z may have interfaces with respectivehigher layers and lower layers (physical layers). A transmitter and areceiver may embody all the link layers A-Z but may select and use onlyone configuration among theses. In some embodiments, the transmitter mayembody at least one link sub layer and when a signal is transmittedusing the link sub layer, the receiver may process only a signal to beprocessed by the receiver among receives signals. Here, link layersignaling may be common to each sub layer and link layer signaling maybe present for each sub layer.

FIG. 122 is a diagram illustrating a method for configuring a link layeron a protocol stack according to another embodiment of the presentinvention.

The present embodiment may correspond to another method for configuringa link layer. The link layer may have a common interface compatible witha higher layer (Link Layer Interface) and a sub layer of each link layermay use a link layer interface.

Each sub layer may have functions for using the common interface. Inaddition, each sub layer may also have an interface with a lower layer(physical layer).

Like in the aforementioned case, the transmitter/receiver may embody allsub layers or embody only some sub layers among these.

FIG. 123 is a diagram illustrating a method for configuring a link layeron a protocol stack according to another embodiment of the presentinvention.

The present embodiment may correspond to another method for configuringa link layer. The link layer may include a sub layer according to aphysical data path (e.g., DP to PLP) owned by a physical layer. Each sublayer may have a corresponding physical data path and may beindependently operated with an independent standard that is appropriatefor the corresponding physical data path.

In some embodiments, respective PLPs may be sub layers but a PLP groupmay be formed and allocated to a sub layer. In this case, the PLP groupmay also be independently operated according to a standard of acorresponding sub layer.

In this case, in this structure, a link layer/sub layer may beconfigured in consideration of an entity for transmitting a PLP, forexample, a broadcasting station. In addition, in some embodiments, alink layer/sub layer may be configured according to the characteristicof transmitted data. For example, when different transmitting entitiesshare the same frequency band and transmit data, if the respectivetransmitting entities intend to transmit data according to differentprotocol/standards, the structure according to the present embodimentmay be applied.

Like in the aforementioned embodiment in which a link layer has a commoninterface with a higher layer, in the present invention, all link layersmay also have a common interface with the higher layer.

FIG. 124 is a diagram illustrating a signaling method for indicating alink layer configuration on a protocol stack according to an embodimentof the present invention.

The aforementioned layer configuration with respect to a link layer andspecific layer may be transmitted to a receiving side via signaling. Alayer by which a corresponding system is configured may be indicated viasignaling, and in particular, a mode in which a specific layer isconfigured may be indicated.

The signaling information may be transmitted using an externaltransmitting method of a corresponding layer. For example, the signalinginformation may be transmitted through a specific signaling channel, anda physical layer may include a dedicated channel for transmitting layerconfiguration signaling information of a link layer. Information aboutthe dedicated signaling channel may be transmitted to the receiving sidevia signaling (PLS, LI, etc.) of the physical layer.

In the aforementioned embodiment of a basic protocol configuring methodor the aforementioned embodiment in which a link layer has a commoninterface with a higher layer, the signaling information may be defined,as illustrated. The signaling information may also be referred to asprotocol configuration information. As described above, the protocolconfiguration information may be added to a signaling portion to beinitially acquired by a receiver, such as physical layer signaling.

In the present embodiment, the protocol configuration information mayinclude Layer_protocol_config (1B) and/or Layer_protocol_version (1B)field. Each field may have a size of 1 byte, which may be changed insome embodiments.

A Layer_protocol_config field may indicate a method in which a specificlayer managed by a corresponding system is operated. In someembodiments, information indicated by each value may be allocated. Forexample, when the field has a value of 0x01, the value may indicate thata link layer has a configuration according to an ATSC link layerprotocol (ALP). When the field has values of 0x02 and 0x03, the valuesmay indicate that the corresponding layer has configurations such as GSEand TLV, respectively. When the field has a value of 0x00, the field maybe reserved for future use.

A Layer_protocol_version field may indicate version information of aprotocol of a layer indicated by the aforementionedLayer_protocol_config field. For example, when the field has a value of0x00, a protocol of the corresponding layer may have an initial version.When the field has values of 0x01, 0x02, protocols of the correspondinglayer may have versions of version 1, version 2, . . . , respectively.

In some embodiments, protocol configuration information may haveadditional information. For example, the protocol configurationinformation may further include information about a layer as a target ofthe signaling information. In addition, in some embodiments, theprotocol configuration information may further include information abouta sub layer as a target of the signaling information. In someembodiments, information of the protocol configuration information maybe added/deleted/changed.

FIG. 125 is a diagram illustrating a signaling method for indicating alink layer configuration on a protocol stack according to anotherembodiment of the present invention.

In the aforementioned embodiment in which an independent physical pathfor each sub layer is provided, the illustrated protocol configurationinformation may be used (t125010 and t125020). Similarly, the protocolconfiguration information may be added to a signaling portion to beinitially acquired by a receiver, such as physical layer signaling.

The protocol configuration information of the illustrated firstembodiment (t125010) may provide different protocol configuration and/orversion information according to respective PLPs. In the presentembodiment, the protocol configuration information may further include aloop according to a Num_DP field and a Num_DP field, a DP_ID field, etc.

A Num_DP (6b) field may indicate the number of DPs that are currentlyprovided. The DP may also be referred to as a PLP. In the presentembodiment, protocols of link layers used for respective PLPs may bedifferent, and thus the field may be included in the protocolconfiguration information in order to provide respective protocolconfiguration information for the respective PLPs. Loops using a forsentence may be generated by as much as the number indicated by thefield. In this loop, protocol information and/or protocol versioninformation of the corresponding sub link layer with respect to each PLPmay be transmitted.

A DP_ID (6b) field may provide ID information of a target PLP to bedescribed by current protocol configuration information. With respect toa PLP indicated by the present field, protocol related information andso on of the sub link layer used in data transmitted by thecorresponding PLP may be provided.

A Layer_protocol_config field and/or a Layer_protocol_version field maybe provided together with the DP_ID field. A description of each fieldis the same as the above description. However, in the presentembodiment, the two fields may provide protocol configurationinformation and/or version information of the protocol of a sub linklayer used in data transmitted by a corresponding PLP with respect tothe PLP identified by the DP_ID field, respectively.

According to the protocol configuration information of this structure, aconfiguration owned by a corresponding system may be indicated. Inparticular, in a receiving system for receiving a plurality of signals,according to the protocol configuration information, layer/sub layerrelated information of a received signal may be acquired.

Sizes (a bit number or the like) of the aforementioned fields may bechanged in some embodiments.

Protocol configuration information of the illustrated first embodiment(t125020) may be protocol configuration information to be used when theaforementioned PLP group and each group is allocated to a sub layer. Inthe present embodiment, the protocol configuration information mayfurther include a loop, a DP_group_ID field, and so on according to theNum_DP_group field and the Num_DP_group field. As such, different linklayer protocol and/or version may be allocated according to each PLPgroup.

A Num_DP_group (6 b) field may indicate the number of PLP groups thatare currently provided. The DP may also be referred to as a PLP. Like inthe aforementioned Num_DP field, a loop using a for sentence may begenerated for each PLP group. Protocol information and/or protocolversion information of a corresponding sub link layer may be transmittedthrough information in the loop.

Separate signaling may be configured with respect to PLPs that belong tothe PLP group. In some embodiments, the protocol configurationinformation according to the present embodiment may contain relatedinformation. In order to indicate the PLPs that belong to the PLP group,PLP IDs of the PLPs that belong to the corresponding PLP group may beused.

A DP_group_ID (6b) field may provide ID information of a target PLPgroup to be stated by the current protocol configuration information.With respect to a PLP group indicated by the field, protocol relatedinformation, etc. of a sub link layer used in data transmitted by PLPsof the corresponding PLP group. A method for identifying PLPs thatbelong to the PLP group has been described above.

A Layer_protocol_config field and/or a Layer_protocol_version field maybe provided together with a DP_group_ID field. A description of eachfield is the same as the above description. However, in the presentembodiment, the two fields may provide protocol configurationinformation and/or version information of the protocol of a sub linklayer used in data transmitted by PLPs of a corresponding PLP group withrespect to the PLP group identified by the DP_group_ID field.

FIG. 126 is a diagram illustrating a method for transmitting a broadcastsignal according to an embodiment of the present invention.

A method for transmitting a broadcast signal according to an embodimentof the present invention may include generating input streams includingservice data about a broadcast service, performing link layerprocessing, physically processing link layer packets, and/ortransmitting the broadcast signal.

A first module of a transmitting side may generate input streamsincluding service data about at least one broadcast service. The firstmodule may manage an operation corresponding to a higher layer on aprotocol stack. The first module may generate service data as a serviceprovider. The service data may be output in the form of various types ofinput streams.

A second module of the transmitting side may link layer process aplurality of input packets. The link layer processing may includeoverhead reduction processing an input stream, and encapsulating inputpackets of the overhead reduction processed input stream as at least onelink layer packet. The link layer processing has been described. Here, apayload of the link layer packet may include a plurality of inputpackets. The input packets may be concatenated and contained in thepayload.

Here, the second module may perform an operation corresponding to a linklayer. The second module may include a first sub block and/or a secondsub block. The first sub block may perform the aforementioned headercompression/overhead reduction step. The first sub block may be a subblock of the second module, which manages an operation of thecorresponding header compression/overhead reduction. The second subblock may perform the aforementioned packet encapsulation. The secondsub block may be a sub block of the second module, which managesencapsulation to a link layer packet.

A third module of the transmitting side may physically process at leastone link layer packet. The third module may mange an operation of aphysical layer. The third module may form a link layer packet as BBpackets and accordingly, may perform processes such as encoding, bitinterleaving, and constellation mapping. Then, processes such as timeinterleaving, frame building, and frequency interleaving may beperformed and a modulation process according to an OFDM method may beperformed.

A fourth module of the transmitting side may transmit a broadcast signalincluding the aforementioned physically processed data. When theaforementioned module performs physical processing to generate abroadcast signal, the fourth module may transmit the broadcast signal tothe receiving side. The fourth module may refer to a transmittingapparatus such as an antenna.

Here, the second module and the fourth module may be included in thethird module. The second, third, and fourth modules may be replaced withone integrated module. The third module may include a plurality ofinternal blocks. The second module may be included in one of the blocksof the third module.

In a method for transmitting a broadcast signal according to anotherembodiment of the present invention, the overhead reduction processingstep may further include deleting a sync byte positioned in a first byteof each input packet. The present step may correspond to theaforementioned sync byte deletion mechanism.

In a method for transmitting a broadcast signal according to anotherembodiment of the present invention, the overhead reduction processingstep may further include deleting null packets included in an inputstream. The present step may correspond to the aforementioned nullpacket deletion mechanism. All various embodiments of the aforementionednull packet deletion mechanisms may correspond to the present step.

In a method for transmitting a broadcast signal according to anotherembodiment of the present invention, the deleting of the null packetsmay further include resetting deleted null packet (DNP) informationincluded in a header of a link layer packet to 0, and deleting the nullpackets positioned in front of an input packet. As described above, nullpackets may be deleted by resetting the DNP to 0 and then increasing theDNP information as the null packets are deleted. This method maycorrespond to a null packet deletion mechanism that does not useinformation such as the aforementioned NPDP.

In a method for transmitting a broadcast signal according to anotherembodiment of the present invention, the DNP information may indicatewhether the step of deleting null packets is performed, and when thestep of deleting null packets is applied, the DNP information mayindicate the number of the deleted null packets. Here, the DNPinformation may correspond to the aforementioned DNP field, and asdescribed above, the DNP field may indicate may also indicate the numberof the deleted null packets as well as whether the null packet deletionmechanism is applied.

In a method for transmitting a broadcast signal according to anotherembodiment of the present invention, the overhead reduction processingstep may further include, when headers of at least two consecutive inputpackets are the same except for counter information, transmitting aheader of a first input packet among the consecutive input packets anddeleting headers of the remaining input packets. The steps maycorrespond to the aforementioned header deleting mechanism for deletingcommon header information.

In a method for transmitting a broadcast signal according to anotherembodiment of the present invention, a header of a link layer packet mayfurther include null packet pointer information, and the null packetpointer information may indicate a position in which the null packetsare deleted. Here, the null packet pointer information may correspond tothe aforementioned NPDP information. This case may correspond to anembodiment of a null packet deletion mechanism when information such asthe aforementioned NPDP is used.

A method for receiving a broadcast signal according to an embodiment ofthe present invention will be described below. The method is notillustrated.

A method for receiving a broadcast signal according to an embodiment ofthe present invention may include receiving a broadcast signal by afirst module of a receiving side, physically processing the broadcastsignal to output link layer packets by a second module of the receivingside, link processing link layer packets to output streams by a thirdmodule of the receiving side, and/or acquiring service data using theoutput stream to provide a service by a fourth module of the receivingside.

Here, the third module of the receiving side may include a first subblock and/or a second sub block. The first sub block may decapsulate alink layer packet to output packets. The second sub block may performopposite processes to compression/overhead reduction schemes applied tothe output packets to recover an original output stream.

The aforementioned physical processing, the link processing, etc. may beopposite processes to those of the transmitting side. The output streammay include a plurality of output packets. In the opposite process, theaforementioned fields may be used. For example, the NUMTS field, etc.may be used in a process for recovering an output stream.

Methods for receiving a broadcast signal according to embodiments of thepresent invention may correspond to the method for transmitting abroadcast signal according to the aforementioned embodiments of thepresent invention. The methods for receiving a broadcast signal may beperformed by hardware modules (e.g., the first, second, third, andfourth modules, and the first and second sub block of a transmittingside) corresponding to modules used in the method for transmitting abroadcast signal. The method for receiving a broadcast signal may haveembodiments corresponding to the aforementioned embodiments of a methodfor transmitting a broadcast signal.

In some embodiments, the aforementioned steps may be omitted or may besubstituted with other steps for performing the same/similar operation.

FIG. 127 is a diagram illustrating an apparatus for transmitting abroadcast signal according to an embodiment of the present invention.

An apparatus for transmitting a broadcast signal according to anembodiment of the present invention may include the aforementionedfirst, second, third, and/or fourth modules of a transmitting side. Adescription of each block and module is the same as the abovedescription.

The apparatus for transmitting a broadcast signal according to anembodiment of the present invention and internal modules/blocks thereofmay perform the methods for transmitting a broadcast signal according tothe aforementioned embodiments of the present invention.

An apparatus for receiving a broadcast signal according to an embodimentof the present invention will be described below. The apparatus is notillustrated.

An apparatus for receiving a broadcast signal according to an embodimentof the present invention may include the aforementioned first, second,third, and/or fourth modules of a receiving side. A description of eachblock and module is the same as the above description.

The apparatus for receiving a broadcast signal according to anembodiment of the present invention and internal modules/blocks thereofmay perform the methods for receiving a broadcast signal according tothe aforementioned embodiments of the present invention.

Block/modules or the like in the aforementioned apparatus may beprocessors for executing consecutive processes stored in a memory or insome embodiments, may be hardware elements positioned inside/outside theapparatus.

In some embodiments, the aforementioned modules may be omitted or may besubstituted with other modules for performing the same/similaroperation.

FIG. 128 is a diagram illustrating a layer structure when a dedicatedchannel is present according to an embodiment of the present invention.

Data transmitted to a dedicated channel may not be an IP packet stream.Accordingly, a separate protocol structure from an existing IP-basedprotocol needs to be applied. Data transmitted to a dedicated channelmay be data for a specific purpose. In the dedicated channel, varioustypes of data may not coexist. In this case, the meaning ofcorresponding data may frequently become clear immediately after areceiver decodes the corresponding data in a physical layer.

In the above situation, it may not be required to process the datatransmitted to the dedicated channel according to all of theaforementioned protocol structures (for normal broadcast data). That is,in a physical layer and/or a link layer, the data transmitted to thededicated channel may be completely processed and information containedin the corresponding data can be used.

In a broadcast system, data transmitted to the dedicated channel may bedata (signaling) for signaling and the data (signaling data) forsignaling may be transmitted directly to a dedicated channel, but not inan IP stream. In this case, a receiver may more rapidly acquire the datatransmitted to the dedicated channel than data transmitted in the IPstream.

With reference to the illustrated protocol structure, a dedicatedchannel may be configured in a physical layer, and a protocol structurerelated to processing of broadcast data of this case is illustrated.

In the present invention, a part that is conformable to a generalprotocol structure may be referred to as a generic part and a protocolpart for processing a dedicated channel may be referred to as adedicated part, but the present invention is not limited thereto. Adescription of processing of broadcast data through a protocol structurein the generic part may be supplemented by the above description of thespecification.

On or more information items (dedicated information A, dedicatedinformation B, and/or dedicated information C) may be transmittedthrough a dedicated part, and corresponding information may betransmitted from outside of a link layer or generated in the link layer.The dedicated part may include one or more dedicated channels. In thededicated part, the data transmitted to the dedicated channel may beprocessed using various methods.

Dedicated information transmitted from outside to a link layer may becollected through a signaling generation and control module in the linklayer and processed in the form appropriate for each dedicated channel.A processing form of the dedicated information transmitted to thededicated channel may be referred to as a dedicated format in thepresent invention. Each dedicated format may include each dedicatedinformation item.

As necessary, data (signaling data) transmitted through the generic partmay be processed in the form of a packet of a protocol of acorresponding link layer. In this process, signaling data transmitted tothe generic part and signaling data transmitted to the dedicated partmay be multiplexed. That is, the signaling generation and control modulemay include a function for performing the aforementioned multiplexing.

When the dedicated channel is a structure that can directly processdedicated information, data in a link layer may be processed by atransparent mode; bypass mode, as described above. An operation may beperformed on some or all of dedicated channels in a transport mode, datain a dedicated part may be processed in a transparent mode, and data ina generic part may be processed in a normal mode. Alternatively, generaldata in the generic part may be processed in a transparent mode and onlysignaling data transmitted to the generic part and data in the dedicatedpart can be processed in a normal mode.

According to an embodiment of the present invention, when a dedicatedchannel is configured and dedicated information is transmitted,processing is not required according to each protocol defined in abroadcast system, and thus information (dedicated information) requiredin a receiving side can be rapidly accessed.

A description of data processing in a generic part and/or higher layersin a link layer illustrated in the drawing may be substituted with theabove description.

FIG. 129 is a diagram illustrating a layer structure when a dedicatedchannel is present according to another embodiment of the presentinvention.

According to another embodiment of the present invention, with respectto some dedicated channels among dedicated channels, a link layer may beprocessed in a transparent mode. That is, processing of data transmittedto some dedicated channels may be omitted in the link layer. Forexample, dedicated information A may not be configured in a separatededicated format and may be transmitted directly to a dedicated channel.This transmitting structure may be used when the dedicated information Ais conformable to a structure that is known in a broadcast system.Examples of the structure that is known in the broadcast system mayinclude a section table and/or a descriptor.

In the embodiment of the present invention, as a wider meaning, whendedicated information corresponds to dedicated information, up to aportion in which the corresponding signaling data is generated may beconsidered as a region of a link layer. That is, dedicated informationmay be generated in the link layer.

FIG. 130 is a diagram illustrating a layer structure when a dedicatedchannel is independently present according to an embodiment of thepresent invention.

The drawing illustrates a protocol structure for processing broadcastdata when a separate signaling generation and control module is notconfigured in a link layer. Each dedicated information item may beprocessed in the form of dedicated format and transmitted to a dedicatedchannel.

Signaling information that is not transmitted to a dedicated channel maybe processed in the form of a link layer packet and transmitted to adata pipe.

A dedicated part may have one or more protocol structure appropriate foreach dedicated channel. When the dedicated part has this structure, aseparate control module is not required in the link layer, and thus itmay be possible to configure a relatively simple system.

In the present embodiment, dedicated information A, dedicatedinformation B, and dedicated information C may be processed according todifferent protocols or the same protocol. For example, the dedicatedformat A, the dedicated format B, and the dedicated format C may havedifferent forms.

According to the present invention, an entity for generating dedicatedinformation can transmit data anytime without consideration ofscheduling of a physical layer and a link layer. As necessary, in thelink layer, data may be processed on some or all of dedicated channelsin a transparent mode or a bypass mode.

A description of data processing in a generic part and/or higher layersin a link layer illustrated in the drawing may be substituted with theabove description.

FIG. 131 is a diagram illustrating a layer structure when a dedicatedchannel is independently present according to another embodiment of thepresent invention.

When the aforementioned dedicated channel is independently present,processing in a link layer may be performed on some dedicated channelsin a transparent mode in an embodiment corresponding to a layerstructure. With reference to the drawing, dedicated information A may betransmitted directly to a dedicated channel rather than being processedin a separate format. This transmitting structure may be used when thededicated information A is conformable to a structure that is known in abroadcast system. Examples of the structure that is known in thebroadcast system may include a section table and/or a descriptor.

In the embodiment of the present invention, as a wider meaning, whendedicated information corresponds to dedicated information, up to aportion in which the corresponding signaling data is generated may beconsidered as a region of a link layer. That is, dedicated informationmay be generated in the link layer.

FIG. 132 is a diagram illustrating a layer structure when a dedicatedchannel transmits specific data according to an embodiment of thepresent invention.

Service level signaling may be bootstrapped to a dedicated channel, or afast information channel (FIC) as information for scanning a serviceand/or an emergency alert channel (EAC) including information foremergency alert may be transmitted. Data transmitted through the FIC maybe referred to as a fast information table (FIT) or a service list table(SLT) and data transmitted through the EAC may be referred to as anemergency alert table (EAT).

A description of information to be contained in a FIT and the FIT may besubstituted with the above description. The FIT may be generated andtransmitted directly by a broadcaster or a plurality of informationitems may be collected and generated in the link layer. When the FIT isgenerated and transmitted by a broadcaster, information for identifyinga corresponding broadcaster may be contained in the FIT. When aplurality of information items are collected to generate an FIT in thelink layer, information for scanning services provided by allbroadcasters may be collected to generate the FIT.

When the FIT is generated and transmitted by a broadcaster, the linklayer may be operated in a transparent mode to directly transmit the FITto an FIC. When the FIT as a combination of a plurality of informationitems owned by a transmitter is generated, generation of the FIT andconfiguration of corresponding information in the form of a table may bewithin an operating range of the link layer.

A description of information to be contained in an EAT and the EAT maybe substituted with the above description. In the case of the EAC, whenan entity (e.g., IPAWS) for managing an emergency alert messagetransmits a corresponding message to a broadcaster, an EAT related tothe corresponding message may be generated and the EAT may betransmitted through the EAC. In this case, generation of a signalingtable based on an emergency alert message may be within an operatingrange of the link layer.

The aforementioned signaling information generated in order to processIP header compression may be transmitted to a data pipe rather thanbeing transmitted through a dedicated channel. In this case, processingfor transmission of corresponding signaling information may beconformable to a protocol of a generic part and may be transmitted inthe form of a general packet (e.g., a link layer packet).

FIG. 133 is a diagram illustrating a format of (or a dedicated format)of data transmitted through a dedicated channel according to anembodiment of the present invention.

When dedicated information transmitted to a dedicated channel is notappropriate for transmission to a corresponding channel or requires anadditional function, the dedicated information may be encapsulated asdata, which can be processed in a physical layer, in a link layer. Inthis case, as described above, a packet structure that is conformable toa protocol of a generic part supported in a link layer may be used. Inmany cases, a function supported by a structure of a packet transmittedthrough a generic part may not be required in a dedicated channel. Inthis case, the corresponding dedicated information may be processed inthe format of the dedicated channel.

For example, in the following cases, the dedicated information may beprocessed in a dedicated format and transmitted to a dedicated channel.

1) When the size of data transmitted to a dedicated channel is notmatched with a size of dedicated information to be transmitted.

2) When dedicated information is configured in the form of data (e.g.,XML) that requires a separate parser instead of a form of a table.

3) When a version of corresponding information needs to be pre-checkedto determine whether corresponding information is processed beforecorresponding data is parsed.

4) When error needs to be detected from dedicated information.

As described above, when dedicated information needs to be processed ina dedicated format, the dedicated format may have the illustrated form.Within a range appropriate to a purpose of each dedicated channel, aheader including some of listed fields may be separately configured anda bit number allocated to a field may be changed.

According to an embodiment of the present invention, a dedicated formatmay include a length field, a data version field, a payload_format field(or a data_format field), a stuffing_flag field, a CRC field, apayload_data_bytes( ) element, a stuffing_length field, and/or astuffing_bytes field.

The length field may indicate a length of data contained in a payload.The length field may indicate the length of data in units of bytes.

The data_version field may indicate a version of information ofcorresponding data. A receiver may check whether the corresponding datais already received information or new information using the versioninformation and determine whether the corresponding information is usedusing the version information.

The data_format field may indicate a format of information contained inthe dedicated information. For example, when the data_format field has avalue of ‘000’, the value may indicate that dedicated information istransmitted in the form of a table. When the data_format field has avalue of ‘001’, the value may indicate that the dedicated information istransmitted in form of a descriptor. When the data_format field has avalue of ‘010’, the value may indicate that the dedicated information istransmitted in form of a binary format instead of a table format or adescriptor form. When the data_format field has a value of ‘011’, thevalue may indicate that the dedicated information is transmitted in formof XML.

When a dedicated channel is larger than dedicated information, astuffing byte may be added in order to match the lengths of requireddata. In this regard, the stuffing_flag field may identify whether thestuffing byte is contained.

The stuffing_length field may indicate the length of the stuffing_bytesfield.

The stuffing_bytes field may be filled with a stuffing byte by as muchas the size indicated by the stuffing_length field. The stuffing_bytesfield may indicate the size of a stuffing byte.

The CRC field may include information for checking error of data to betransmitted to a dedicated channel. The CRC field may be calculatedusing information (or a field) contained in dedicated information. Upondetermining that the error is detected using the CRC field, a receivermay disregard received information.

FIG. 134 is a diagram illustrating configuration information of adedicated channel for signaling information about a dedicated channelaccording to an embodiment of the present invention.

In general, determination of an operation in a transparent mode or anormal mode with respect to the aforementioned dedicated channel may bepre-determined during design of a dedicated channel and may not bechanged during management of a system. However, since a plurality oftransmitting systems and a plurality of receiving systems are present ina broadcast system, there may be a need to flexibly adjust a processingmode for a dedicated channel. In order to change or reconfigure anoperating mode of a flexible system and provide information about theoperating mode to a receiving side, signaling information may be used.The signaling information may be contained in a physical layersignaling; L1 signaling; transmitting parameter and transmitted, and maybe transmitted to one specific dedicated channel. Alternatively, thesignaling information may be contained in a portion of a descriptor or atable used in a broadcast system. That is, the information may becontained as a portion of one or more signaling information itemsdescribed in the specification.

The dedicated channel configuration information may include anum_dedicated_channel field, a dedicated_channel_id field, and/or anoperation_mode field.

The num_dedicated_channel field may indicate the number of dedicatedchannels contained in a physical layer.

The dedicated_channel_id field may correspond to an identifier foridentifying a dedicated channel. As necessary, an arbitrary identifier(ID) may be applied to a dedicated channel.

The operation_mode field may indicate a processing mode for a dedicatedchannel. For example, when the operation_mode field has a value of‘0000’, the value may indicate that the dedicated channel is processedin a normal mode. When the operation_mode field has a value of ‘1111’,the value may indicate that the dedicated channel is processed in atransparent mode or a bypass mode. ‘0001’ to ‘1110’ among values of theoperation_mode field may be reserved for future use.

FIG. 135 is a flowchart illustrating a broadcast signal transmissionprocessing method according to an embodiment of the present invention.

A broadcast transmitter may perform header compression on headers offirst IP packets including first broadcast data (JS12810).

The broadcast transmitter may generate first link layer packetsincluding the first IP packets on which the header compression isperformed and second link layer packets including second IP packetsincluding second broadcast data (JS128020).

The broadcast transmitter may generate third link layer packetsincluding link layer signaling information for providing informationrequired to process the first link layer packets and the second linklayer packets (JS128030). The link layer signaling information mayinclude compression flag information for identifying whether the headercompression is performed on the first IP packets or the second IPpackets.

The broadcast transmitter may generate one or more broadcast framesincluding the first link layer packets, the second link layer packets,and the third link layer packets (JS128040).

The broadcast transmitter may generate a broadcast signal including theone or more broadcast frames (JS128050).

The broadcast transmitter may generate first dedicated information,generate second dedicated information, generate a dedicated formatpacket including the second dedicated information, transmit the firstdedicated information to a first dedicated channel as a specific regionin the broadcast signal, and transmit the dedicated format packet to asecond dedicated channel as a specific region in the broadcast signal.Here, the first dedicated information or the second dedicatedinformation may correspond to information required to scan one or morebroadcast channels and to acquire a broadcast service or information forperforming emergency alert.

The broadcast signal may further include dedicated channel configurationinformation including information related to processing of a dedicatedchannel, and the dedicated channel configuration information may includededicated channel number information for identifying the number ofdedicated channels contained in the broadcast signal.

The dedicated channel configuration information may further includededicated channel identification information for identifying thededicated channel and may further include operating mode information foridentifying whether the first dedicated information and the seconddedicated information, which are transmitted to the dedicated channel,are encapsulated in the dedicated format packet. Here, the dedicatedchannel configuration information may be included in the link layersignaling information.

The dedicated format packet may further include data format informationfor identifying a form of information for forming the second dedicatedinformation.

FIG. 136 is a diagram illustrating a broadcast system according to anembodiment of the present invention.

The broadcast system may include a broadcast transmitter J129100 and/ora broadcast receiver J129200.

The broadcast transmitter J129100 may include a processor J129110, abroadcast signal generator J129120, and/or a transmitter J129130.

The processor J129110 may include a link layer processor J129112 and/ora physical layer processor J129114.

The broadcast receiver J129200 may include a receiver J129210, abroadcast signal decoder J129220, and/or a decoder J129240.

The decoder J129240 may include a physical layer decoder J129242 and/ora link layer decoder J129244.

The processor J129110 may perform a series of processing on datacontained in a broadcast service.

The link layer processor J129112 may process broadcast data in a linklayer. An operation of the link layer processor J129112 may be performedby the processor J129110, and in this case, the link layer processorJ129112 may not be separately included.

The link layer processor J129112 may perform header compression onheaders of first IP packets containing first broadcast data, generatefirst link layer packets including the first IP packets on the headercompression is performed and second link layer packets including secondIP packets including second broadcast data, and generate third linklayer packets including link layer signaling information for providinginformation required to process the first link layer packets and thesecond link layer packets. Here, the link layer signaling informationmay include compression flag information for identifying whether theheader compression is performed on the first IP packets or the second IPpackets.

The physical layer processor J129114 may process broadcast data in aphysical layer. An operation of the physical layer processor J129114 maybe performed by the processor J129110, and in this case, the physicallayer processor J129114 may not be separately included. The physicallayer processor J129114 has been described with regard to a process forprocessing data in a physical layer in the specification.

The physical layer processor J129114 may generate one or more broadcastframes including the first link layer packets, the second link layerpackets, and the third link layer packets.

The broadcast signal generator J129120 may generate a broadcast signal.As necessary, the broadcast signal may be generated by the physicallayer processor J129114 and in this case, it may be deemed that thebroadcast signal generator J129120 is included in the physical layerprocessor J129114.

The transmitter J129130 may transmit the broadcast signal. Thetransmitter J129130 may receive a request of the broadcast receiverJ129200.

The receiver J129210 may receive the broadcast signal. The receiverJ129210 may transmit the request to the broadcast transmitter J129100.

The broadcast signal decoder J129220 may decode the broadcast signal.

The decoder J129240 may perform a series of processing on broadcast datain order to embody a broadcast service.

The physical layer decoder J129242 may decode data in the physicallayer. A function of the physical layer decoder J129242 may be performedby the decoder J129240 and in this case, the physical layer decoderJ129242 may not be separately included.

The link layer decoder J129244 may decode data in a link layer. Afunction of the link layer decoder J129244 may be performed by thedecoder J129240 and in this case, the link layer decoder J129244 may notbe separately included.

Modules or units may be processors executing consecutive processesstored in a memory (or a storage unit). The steps described in theaforementioned embodiments can be performed by hardware/processors.Modules/blocks/units described in the above embodiments can operate ashardware/processors. The methods proposed by the present invention canbe executed as code. Such code can be written on a processor-readablestorage medium and thus can be read by a processor provided by anapparatus.

While the embodiments have been described with reference to respectivedrawings for convenience, embodiments may be combined to implement a newembodiment. In addition, designing a computer-readable recording mediumstoring programs for implementing the aforementioned embodiments iswithin the scope of the present invention.

The apparatus and method according to the present invention are notlimited to the configurations and methods of the above-describedembodiments and all or some of the embodiments may be selectivelycombined to obtain various modifications.

The methods proposed by the present invention may be implemented asprocessor-readable code stored in a processor-readable recording mediumincluded in a network device. The processor-readable recording mediumincludes all kinds of recording media storing data readable by aprocessor. Examples of the processor-readable recording medium include aROM, a RAM, a CD-ROM, a magnetic tape, a floppy disk, an optical datastorage device and the like, and implementation as carrier waves such astransmission over the Internet. In addition, the processor-readablerecording medium may be distributed to computer systems connectedthrough a network, stored and executed as code readable in a distributedmanner.

Although the preferred embodiments of the present invention have beendisclosed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the inventionas disclosed in the accompanying claims. Such modifications should notbe individually understood from the technical spirit or prospect of thepresent invention.

Both apparatus and method inventions are mentioned in this specificationand descriptions of both the apparatus and method inventions may becomplementarily applied to each other.

Those skilled in the art will appreciate that the present invention maybe carried out in other specific ways than those set forth hereinwithout departing from the spirit and essential characteristics of thepresent invention. Therefore, the scope of the invention should bedetermined by the appended claims and their legal equivalents, not bythe above description, and all changes coming within the meaning andequivalency range of the appended claims are intended to be embracedtherein.

In the specification, both the apparatus invention and the methodinvention are mentioned and description of both the apparatus inventionand the method invention can be applied complementarily.

Various embodiments have been described in the best mode for carryingout the invention.

The present invention is applied to broadcast signal providing fields.

Various equivalent modifications are possible within the spirit andscope of the present invention, as those skilled in the relevant artwill recognize and appreciate. Accordingly, it is intended that thepresent invention cover the modifications and variations of thisinvention provided they come within the scope of the appended claims andtheir equivalents.

The invention claimed is:
 1. A method for transmitting a broadcastsignal, the method comprising: generating an input stream includingservice data of a broadcast service, the input stream including aplurality of input packets; link layer processing the input stream,wherein the link layer processing comprises: overhead reductionprocessing the input stream, and encapsulating the input packets of theoverhead reduction processed input stream to a link layer packet,wherein the link layer packet includes a base header and a payload,wherein the base header includes an additional header flag fieldindicating whether an additional header is present following the baseheader, wherein the additional header follows the base header in thelink layer packet when a value of the additional header flag field isset to 1, and wherein the payload carries the encapsulated inputpackets; and transmitting a broadcast signal carrying the link layerpacket, wherein the overhead reduction processing further comprisesdeleting null packets included in the input stream, wherein the deletingthe null packets further comprises: re-setting a counter for null packetdeletion to 0; and deleting the null packets until a first non-nullinput packet appears in the input stream while incrementing a value ofthe counter for each of the null packets deleted, the null packets beinglocated in front of the first non-null input packet, wherein successiveinput packets starting from the first non-null input packet in the inputstream are encapsulated into the payload of the link layer packet, thevalue of the counter is used to determine a value of a Deleted NullPacket (DNP) field in the additional header of the link layer packet,and the DNP field indicates a number of the deleted null packets,wherein the additional header includes a header compression flag fieldindicating whether header deletion of the successive input packets isapplied, and wherein when the header compression flag field indicatesthat the header deletion is applied and headers of the successive inputpackets have the same information, the overhead reduction processingfurther comprises: locating, in the payload of the link layer packet, aheader of a first input packet among the successive input packets; anddeleting headers of the rest of the successive input packets.
 2. Themethod according to claim 1, wherein the DNP field further indicateswhether the deleting the null packets is conducted.
 3. An apparatus fortransmitting a broadcast signal, the apparatus comprising: a processorconfigured to: generate an input stream including service data of abroadcast service, the input stream including a plurality of inputpackets, and link layer process the input stream, wherein, to link layerprocess the input stream, the processor is further configured to:overhead reduction process the input stream, and encapsulate the inputpackets of the overhead reduction processed input stream to a link layerpacket, wherein the link layer packet includes a base header and apayload, wherein the base header includes an additional header flagfield indicating whether an additional header is present following thebase header, wherein the additional header follows the base header inthe link layer packet when a value of the additional header flag fieldis set to 1, and wherein the payload carries the encapsulated inputpackets; and a transmitter configured to transmit a broadcast signalcarrying the link layer packet, wherein, to overhead reduction processthe input stream, the processor is further configured to delete nullpackets included in the input stream, wherein, to delete the nullpackets, the processor is further configured to: re-set a counter fornull packet deletion to 0, and delete the null packets until a firstnon-null input packet appears in the input stream while incrementing avalue of the counter for each of the null packets deleted, the nullpackets being located in front of the first non-null input packet,wherein successive input packets starting from the first non-null inputpacket in the input stream are encapsulated into the payload of the linklayer packet, and the value of the counter is used to determine a valueof a Deleted Null Packet (DNP) field in the additional header of thelink layer packet, and the DNP field indicates a number of the deletednull packets, wherein the additional header includes a headercompression flag field indicating whether header deletion of thesuccessive input packets is applied, and wherein when a value of theheader compression flag field is set to 1 and headers of the successiveinput packets have the same information, the overhead reductionprocessing further comprises: locating, in the payload of the link layerpacket, a header of a first input packet among the successive inputpackets; and deleting headers of the rest of the successive inputpackets.
 4. The apparatus according to claim 3, wherein the DNP fieldfurther indicates whether the processor deleted the null packets.
 5. Anapparatus for receiving a broadcast signal, the apparatus comprising: atuner configured to receive the broadcast signal including a link layerpacket, the link layer packet including a base header and a payload,wherein the base header includes an additional header flag fieldindicating whether an additional header is present following the baseheader, wherein the payload carries input packets, wherein theadditional header follows the base header in the link layer packet whena value of the additional header flag field is set to 1, and wherein theadditional header includes a Deleted Null Packet (DNP) field and aheader compression flag field, the DNP field indicating a number ofdeleted null packets, the header compression flag field indicatingwhether header deletion of the input packets is applied; and a processorconfigured to decapsulate the link layer packet, wherein all inputpacket headers are recovered based on a header of a first input packetamong the input packets when the header compression flag field indicatesthat the header deletion is applied, and wherein the deleted nullpackets are recovered based on the DNP field.
 6. A method for receivinga broadcast signal, the method comprising: receiving the broadcastsignal including a link layer packet, the link layer packet including abase header and a payload, wherein the base header includes anadditional header flag field indicating whether an additional header ispresent following the base header, wherein the payload carries inputpackets, wherein the additional header follows the base header in thelink layer packet when a value of the additional header flag field isset to 1, and wherein the additional header includes a Deleted NullPacket (DNP) field and a header compression flag field, the DNP fieldindicating a number of deleted null packets, the header compression flagfield indicating whether header deletion of the input packets isapplied; and decapsulating the link layer packet, wherein all inputpacket headers are recovered based on a header of a first input packetamong the input packets when the header compression flag field indicatesthat the header deletion is applied, and wherein the deleted nullpackets are recovered based on the DNP field.